Undertale Yellow react to...

Unlike Undertale, the neutral path can only be reached if the player kills at least one monster.

Clover falls into a Underground and immediately encounters Toriel, who promises to guide them through the puzzles. However, during one of these puzzles, something goes wrong. The passage won't open, and Clover falls through the ground. Toriel tells them to stay put while she figures out a way to get them out, but Clover ignores her and goes into the Dark Ruins.

In the Dark Ruins, Clover meets Flowey, who tells them about the dungeon and teaches them how to fight monsters. Later, the protagonist encounters a mysterious monster, who talks to himself and complains about child interrupting his monologue. After this, Clover finds themself in a maze, which is actually a cornfield. After escaping, they are again confronted by the mysterious monster. He begins a monologue, but this time he stops it as soon as he sees human, then goes home to sleep.

After another dialogue with the mysterious monster, the protagonist finds themselves in a long passageway where they are attacked by Decibat, who, after a battle with Clover, names them Lord of Silence and flies off to spread further silence. After several puzzles, child encounters the mysterious monster again, who asks them to leave, but Clover continues to follow, prompting the mysterious monster to engage in battle. It is revealed that the mysterious monster's name is Dalv. After the battle, Clover can enter the house (or it will invite you) where the door to Snowdin is located.

In Snowdin, Clover encounters the Martlet puzzles for the first time, which they must solve along the way. At the very end, Clover encounters the Martlet itself, who, realizing Clover is human, engages in combat, following the Royal Guard Code. However, the fight turns out to be completely different than she expected, as Clover doesn't attack her, as the code should have.

Feeling that she's doing wrong by attacking Clover and receiving no response, she begins asking them to insult her. However, Clover's insults prove harmless and entirely justified, so she ends the fight. Since the Martlet has violated the Guardian Code, she decides to help Clover escape the Underground without anyone knowing of her failure. She and Clover travel on a boat down the river that is supposed to take them to Hotland. However, the river proves too swift, causing Clover to fall into a cave, and the Martlet to fly away, trying to find help.

After falling, Clover encounters Flowey again, who blames the Martlet for everything that happened and tells them not to trust anyone. After exiting the cave, Clover finds themselves in the Dunes.

Some time later, Clover meets the Martlet again, who promises to help them, but they are forced to split up again when Clover reaches the town "Wild East." At the entrance, they encounter the "Feisty Five"— Ed, Moray, Ace, Mooch, and North Star. Initially, they want to let the heroes pass, but then North Star realizes Clover is human and decides to forcibly convert them to the "Feisty Five," transforming them into the "Feisty Six." The Martlet tries to stop them from kidnapping Clover, but proves incapable of doing anything and is imprisoned in the local prison. In the town, Clover meets North Star's childhood friend Ceroba, who is quite friendly and tells them a little about the "kidnapper." North Star himself begins to prepare Clover to become a member of the Five, giving them very stupid and easy tasks, which, however, anger the other four members, who had to go through much more serious trials. The climax comes when, after these tasks, North Star appoints Clover as the city's deputy, a much higher position than that of a member of the Feisty Five, so Ed, Moray, Ace, and Mooch decide to give Clover a "true test" — a battle — while North Star isn't looking.

However, he finds out, and a scandal ensues, resulting in North Star's true identity — Starlo — being revealed, and the Feisty Five disband. The Four say Starlo has changed a lot since he began ruling the Wild East, and Starlo accuses them of envy. After all four leave, Starlo tries to ask for support from Ceroba, who has approached, but she, too, sides with the Four. Starlo leaves and tries to figure out what he needs to do.

When Clover finds Starlo, he initially ponders why his efforts to entertain the Town ended so badly, but when he finds Clover, he first blames them for everything, then decides that if he "does the job of a Royal Guard," he will be respected not only in the Wild East, but throughout the Underground. Starlo lassoes Clover and begins a fight. Clover manages to break free, but then Starlo draws a revolver. The last bullet would have surely killed Clover, but Ceroba arrives just in time to revive Starlo. Meanwhile, Martlet is freed from its cage, but she hesitates to follow Clover due to being away from her post for too long.

After numerous puzzles and bosses in Steamworks, Clover arrives at the Hotel in Hotland. Entering the area where Bratty and Catty were, They will find an empty room with a trash can and a "Flowey Save." Flowey interrupts Clover's walk to the rooftop, informing them this isn't the way to the castle, asking them to turn back and continue the plan. When Clover ignores him, he says the letter from the Steamworks is likely a trap and asks if they're so dumb as to fall for that, saying that bird never got them anywhere, but eventually gives in and lets them meet with her. Either way, Martlet offers for Clover to live with her in a "happy, violence-free childhood", believing they can change for the better and end the conflict, which Clover either agrees to, or stays silent about, with dialogue choices that change based on their LOVE/EXP.

Both options lead to Martlet preparing to take Clover to Snowdin before being impaled by a vine sent by Flowey. She assumes it was Clover and either asks why, or says she should have known before dying, prompting Flowey to face Clover. He then kills Clover and takes their soul, though Clover still holds on to their sense of self. He talks to them, reminding them about their simple plan to go to ASGORE, and that they've always been predictable. He then reveals this run is in the hundreds as any other run, Clover either stayed with Toriel, or died outside the Ruins. So to steer them off that path, Flowey tampered with the switches to bring them to the Dark Ruins. He then grows surprised Clover is still here, thinking they would have given up after his boring story, but then fights them. After the fight, Flowey calls them annoying for not giving up and lying down, though he admits it was fun for a moment. Flowey decides to "cut a deal" and reset the timeline back to when Clover first fell down, though he may try to take their soul again if they end up in the same scenario, and advises them to make different choices, as "this outcome sucks" and this isn't what he's truly looking for.

Through repeating fights and killing enough monsters, Clover can initiate the Genocide route, enacting a Monster genocide in the areas of Undertale Yellow's Underground in an attempt to become strong enough to defeat Asgore, save the 5 previously captured human SOULs and pass through the Barrier to exit the Underground.

At the start, nothing very relevant happens. Dalv's monologues remain the same, enemy encounters continue triggering, and puzzles still have to be fully solved. However, if the player continues their Genocide Route until they kill 13 Dark Ruins enemies (not counting unique encounters), the normal battle music is replaced with Enemy Retreating along with Flowey's save point dialogue changing to state how many monsters are left until the kill count is exhausted. With each kill, the pitch and speed for Enemy Retreating lower after the battle is over.
If the player exhausts the Dark Ruins kill counter before the fight with Decibat would normally play out, the fight is skipped entirely.
Flowey will appear after killing the last monster in the Dark Ruins, saying that Clover "is not for that mercy thing", but reassuring them that he's their friend, saying that real friends don't judge each other. Flowey's dialogue also suggests that Clover briefly thought about killing Flowey before he reminded them that he's the only reason Clover can save. After this, the overworld music will slow down and lower in pitch.
Even after Enemy Retreating and Flowey's appearance, Dalv's final monologue before his battle will remain the same.
However, when the battle starts, his dialogue will be entirely different. He will mention that he despite his desire to be left alone, that he noticed dust lying all over the Dark Ruins, and that nobody comes to his house anymore. He admits that he wished for everyone to be gone and that he should thank Clover for their actions, only to realize that he now misses the late monsters.

Dalv will then mention how he regrets never trying to befriend the monsters in the Dark Ruins and begins to wonder if his wish for them to disappear was somehow granted, making Clover a figment of his imagination, and the entire battle a dream. Upon meeting his death, however, he realizes that Clover is indeed real and that when he wakes up, Clover will still be there. He realizes that it's likely he just won't wake up at all, before dying as he turns to dust.

When Dalv is killed, Clover will have access to the entire house, including Dalv's previously inaccessible bedroom which includes a journal containing a single entry. The descriptions of the items will be much crueler, and if the wardrobe is opened, Pops's helium will be sucked in by Clover, making them sound funny for a while. Just like in the Neutral Route (if Dalv is dead), Flowey will break the planks for Clover to pass.

In Snowdin, at this point in the run, consumable items will stop having flavor text upon being eaten, and will only display how much HP was healed.
Slurpy's side-quest can't be completed since most of the necessary NPCs have been evacuated.

When the kill counter is exhausted, most of Snowdin's NPCs will be evacuated, with the exception being the band inside Honeydew Resort.
To continue the Genocide Route, Clover must exhaust the kill counter before attempting to fight Martlet.
Martlet's battle is significantly more difficult.
Her AT is higher (8 in Neutral, 12 in Genocide Route) but her DF is lower (10 in Neutral, 8 in Genocide Route).
The bullet patterns closely resemble those of her usual battle, but employ additional projectiles and more rapid attacks.

Dunes:
The only thing changed from the Pacifist/Neutral Route at first is that almost all NPCs have disappeared. The Monster outside the East Mine leaving for Snowdin, the one outside the jammed elevator, and Moray's parents are the only ones you will encounter.

The first of these is seemingly off-put by child's appearance, being a lot more apologetic after bumping into them, and stammering a little. Moray's parents offer to let them stay in the headquarters, implying that news of human hasn't reached the Dunes yet.
Before the El Bailador fight, there is a conversation with Flowey about how if Clover is excited that they have come this far, the only option being to reply with "...", making Flowey a bit discomforted. He mentions how them are harder to read, and gloomy, before dismissing it and letting them save.
The El Bailador fight is changed entirely, with their SOUL being outside the box it was confined in. Instead, them dodge the descending "Note Bars" from inside their box, with free movement, with the notes getting knocked away at the bottom of the box instead. Coupled with the fact El Bailador gets very disheartened halfway through the fight, it makes things much easier than in the Pacifist run of this fight. Though if the kill counter has been exhausted before heading to him, the fight will not happen.
If Clover has not killed all enemies before heading into Oasis Valley, a pop-up will appear that says "There are still enemies to bring justice on.", allowing you to turn around and check again.

After this checkpoint, Martlet will approach Clover, pleading, and trying to empathize with them. She also mentions that the rest of the Royal Guard are looking for them, and they're lucky it was HER who found them. Twice, Clover interrupt her. First, by stepping forward, then by pointing their gun at her. This prompts her to leave. On the road approaching the Wild East, the Wild Revolver will be sitting on the ground. Upon taking it, it will be equipped and the Toy Gun will be thrown away automatically.
Upon entering the Wild East area, Starlo approaches Clover, trying to settle things with a clean, moral duel.

Regardless of if Clover try to fire or not, Starlo will end up shot, and after that human shot him in return, living sheriff with deadly blow. Ceroba approaching him to comfort him before Starlo turn to dust, not before telling Ceroba to deliver justice. Afterwards, a fight with her will occur. This will prove difficult, as both phases of her fight have attacks that will temporarily reduce your Max HP for the rest of the fight. Dodging red-colored attacks will be key to avoiding that, and refraining from touching the walls of the battle box will become necessary in Phase 2 of the fight.

Steamworks:
Clover quickly shoots the panel to unlock the Steamworks gate while Flowey is talking.
Clover tries to shoot the generator, which upsets Flowey, prompting him to state that bullets aren't always the answer to their problems. Clover quickly strongarms Flowey into breaking down the door instead, skipping two puzzles.
Most of Clover and Axis's encounters have them switch places in contrast to the Pacifist/Neutral Route.
Axis tries to attack Clover during their first encounter due to their vandalism, which results in Clover swiftly shooting off the left side of Axis's face. Axis makes his escape through the trapdoor, saying that he must evacuate the others.
During their second encounter, Axis flees while Clover pursues him instead. Axis is then absent from the long hallway afterwards.
Axis is absent from the third encounter - after Clover uses the Hydrochloric Acid.
Axis's boss fight has Axis wielding the trash can lid instead.

Clover treats Flowey a lot more coldly after this point, commanding him to move things for them, and even walking threateningly towards him.
Macro Froggit will not come out of the door and fight Clover if the unlock requirements are met. Instead, a Micro Froggit will toss out the chest with the Golden Bandana and leave.

Clover cannot purchase items from Mo, as Clover instantly points their gun at him when he tries to speak. They can then choose to rob him of his hundreds of G or not. This is optional to the Genocide Route.
Seeing as the child will likely have a lot of G at this point, and considering how G is never truly relevant in Genocide, there's never really any reason to rob Mo.
Clover being unwilling to kill Mo can also be interpreted as Clover, even on this route, having a "code" of honor, only ever attacking monsters who attack them or don't surrender. This claim can be backed up with Clover letting Martlet escape twice (even when it turns to their detriment in the long run).

Vendy hasn't fled since they are a stationary machine, but much like the other vendors, it will still give you all its items for free, like any other vendor in the Route.

Approaching Guardener will play a cutscene where Axis reassures Guardener and tells her to stay hidden. Guardener then spots Clover and quickly hides.
If Clover has not yet killed all robots by the time you reach the computer room preceding Axis, you will abort the Genocide Route, and this is the last point at which you can do this.

Axis takes the trash can lid during their boss battle instead of Clover. He cannot be damaged during this fight as he blocks all attacks and all Clover's attacks deal 0 damage. Because of this, Glass Bullets will not heal you upon hit.
After finishing the final attack, Axis will attempt to explain and apologize to Clover, as his protocol forced him to kill one of the fallen humans. At this point, all health will be restored, and Clover will rapidly level to LV 19, SOUL turning upside down to fire a bullet at the trash lid, blowing it away before firing again, destroying Axis.

When Clover enters Bits and Bites, the normal shopkeep is not present. However, a strange figure can be seen in the background.
Clover meets with Martlet on the rooftop.

In a desperate attempt to stop Clover, she injects herself with the determination syringe and transforms into her "Zenith of all Monsterkind" form, engaging Clover in a two-phase fight.
Clover will be fully healed upon entering the second phase.

Once Martlet has been killed, Clover's LV reaches 20. With more determination than Flowey, Clover easily foils Flowey's attempts to sabotage their plans or escape. Flowey resorts to taunting Clover, before they ultimately shoot Flowey to death.
Following this, Clover travels to the Castle, encountering Asgore. After speaking to Clover of the consequences of their actions, he attempts to destroy Clover's SOUL with his trident, only for the weapon to be shattered upon impact. Clover then vaporizes Asgore with a laser beam emitting from their SOUL. They then absorb Asgore's SOUL, collect the five other human SOULs, and proceed to exit the Underground.

In this route, the final boss is Ceroba Ketsukane. Depending on whether the player spares or kills her, it ends with the True Pacifist or Flawed Pacifist ending.

Given the ending of the route, it's likely that the True Pacifist ending is the one that's canon in relation to the events that occur in Undertale. This is because, at the end of this route, Martlet and Starlo put the Nice hat and Wild Revolver on a raft, and later they fall into the garbage dump. Then, in Undertale, Bratty and Catty claim that they found these items there.

After sparing an area's boss, all enemies in that respective area become NPCs throughout the area for Clover to talk to when they backtrack. This is exclusive to the Pacifist Route.

Dark Ruins:
When Clover is ready to leave, Dalv tells them that he plans to go to Snowdin after he packs up and leaves the Dark Ruins, which he says will take a few days.

Snowdin:
Snowdin in the Pacifist Route is identical to a Neutral Route in which no monsters were killed in the area.

Dunes:
During Ceroba's introduction at the Wild East, she is more friendly to Clover than she is on a Neutral Route and expresses that she wants to help them leave the Wild East.

After reaching the Sunnyside Farm and gaining access to Fast Travel, Clover can receive a letter from Dalv telling them that he moved to Snowdin. If Clover travels back to Snowdin at this point, they can find Dalv and other Dark Ruins monsters throughout Snowdin.

Steamworks:
Ceroba goes with Clover through the Steamworks, wanting them to travel with her to the Lab to find Kanako. This results in a different path than in other routes.

Ceroba takes Flowey's place in most of the Steamworks' cutscenes. Flowey does not appear at SAVE points and only appears to talk to Clover when they are alone, during which he tries to convince them not to trust Ceroba.
Ceroba interjects into many cutscenes and different dialogue in the environment.

Ceroba shields Clover's SOUL to make them invulnerable for one hit in battles when she is present, signified by a diamond appearing over their SOUL at the start of the enemy's turn. The exceptions to this are:
Macro Froggit, who Clover gets no shield against,
Axis, who Clover only gets shielded against at the very end of his fight,
and Guardener, who Clover only gets shielded against when all the menus are freed.
The UGPS stations cannot be used when Ceroba is with Clover, as she does not want to bring attention to them. This prevents Clover from obtaining Mail or using Fast Travel, which they would otherwise have access to on a Neutral Route without Ceroba accompanying them. They can use the stations again once separated from Ceroba at the end of the Steamworks.
After falling through the trapdoor, Ceroba comes with an idea to build a "companion" for Axis as she is reluctant to fight him since Chujin built him. Clover builds Daisy using the junk around the room, which Ceroba holds on to.
Ceroba uses Chujin's passcode to enter the Factory Wing at the crossroads. This path is exclusive to this route, as other routes lead Clover into the Chemistry Wing.

Mr. Screen appears throughout the Factory Wing and forces them to box and sort goods to progress.
On the third floor, Clover and Ceroba have to sneak around the room and avoid Axis to find a door code by lighting furnaces. If Axis catches them, they are thrown down an elevator shaft to the first floor and have to return to the third floor to retry.
On the fourth floor, the door passcode is behind the manager's desk. Ceroba stops to read Chujin's performance reports about Axis's repeated failures. She is saddened that Chujin never shared this with her and is furious towards Asgore doubting him.
After draining Axis's entire battery, he can be spared through 'Plan B' ACT, where he becomes infatuated with Daisy.

As Ceroba prepares to lead Clover to the Lab, they are stopped by Starlo and Ed, who discovered a trapdoor leading to a bunker full of incriminating research while preparing a party for Kanako's return. When Starlo demands to know what Ceroba is planning, she flees through the elevator, with Starlo chasing after her. Before leaving, Starlo orders Ed to take Clover back to the Wild East.

Once back, the others Feisty Four members show up. Martlet arrives as well, as she was contacted by Moray. Martlet convinces Ed to have Clover follow her to the Estate to investigate while he explains what he knows to the group.

At the Estate, they locate the trapdoor Ed discovered. They enter Chujin's secret study and watch his video journal. These videotapes detail his plans to create a serum allowing any monster to become as strong as a Boss Monster, which led to him experimenting on himself and causing his demise. His last tape is him telling Ceroba to find a human with a pure SOUL and kill them to finish his work. Horrified, Martlet takes Clover out of the Estate and meets up with the Feisty Four, convincing them that she and Clover need to go and stop Ceroba. She flies ahead to Hotland and the Feisty Four wish Clover luck. Clover begins to walk away but is stopped by Flowey, who mocks them for trusting Ceroba. However, rather than continuing to tell them to leave Ceroba, Flowey says that he supports Clover and is curious about what will happen next.

At UG Apartments, Clover meets up with Martlet on its roof. She explains where Ceroba and Starlo are. She tells Clover that they are a kind and peaceful person in spite of all their hardships, contrasting what she was told as a Royal Guard. She then promises Clover that after they diffuse the conflict with Ceroba, she will convince Asgore to let Clover free and promises to meet them again when the barrier one day breaks. The two head to New Home.

Once there, they find Starlo and Ceroba in a standoff, where Ceroba reveals that she believes Kanako is dead. Despite both Martlet and Starlo's attempts, Ceroba refuses to back down. Martlet attempts to flee with Clover, but Ceroba knocks out both her and Starlo with little effort. She goes on to state that Clover, while admirable, is naïve for thinking that the five humans can be saved or that Asgore would let Clover go. Admitting to be a hypocrite and no better than Asgore on morality, she reasserts she will protect Monsterkind by completing Chujin's work.

She and Clover then fight. At first, Clover survives Ceroba's attacks, but once brought to the tipping point, she assaults them with a barrage of attacks. Before the last hit can strike, Clover unlocks the Yellow SOUL mode and blasts back. Realizing the situation, she puts on Kanako's mask and takes a kitsune-like form. Clover eventually cracks the mask, which causes a memory to play out before the two of them. The memory is of Chujin on his deathbed, who tells Ceroba of the bunker where he worked on his project, with Kanako having heard everything. Ceroba is initially startled by Clover being in her head, but continues fighting. Clover manages to chip away more of the mask, revealing another memory of Kanako and Ceroba in Chujin's bunker. In this memory, Kanako finds out about Ceroba's plan to create a Boss Monster serum. Ceroba's note, which she threw in the garbage, alleges that she removed any corruption Chujin's previously used serum held, and so Kanako pleads Ceroba to volunteer as a Boss Monster in the experiment. Ceroba then injects Kanako with the serum, causing her to fall down. As Ceroba lays silently before Clover, she states she knows she is unforgivable but is unable to let go, and gets up one last time.

Eventually, Clover manages to overwhelm and destroy the mask, reverting Ceroba back to her normal state.

As she lays defeated before Clover, she realizes her attempts at fulfilling Chujin's legacy costed her family, and made her attack her friends and a child, for a plan that may not even work. Racked with guilt, she begs Clover to finish her. In the final scene of the battle, Clover is only given options to kill or spare Ceroba, where sparing leads to the True Pacifist Ending, and killing leads to the Flawed Pacifist Ending.

The True Pacifist Ending is reached by selecting the Mercy option 3 times at the end of the final battle against Ceroba. Ceroba, confused as to why Clover is sparing her, is interrupted by Starlo waking up and brushes off her concerns as payback for how he acted back in the Wild East. Martlet wakes up as well and tries to help Clover escape before Ceroba calms her down by revealing that Clover already won the fight. Ceroba then apologizes for how she acted, having been too obsessed in her quest to fulfill Chujin's legacy, before being comforted by Starlo. Martlet also promises to use her Royal Guard connections to the royal scientist to locate Kanako. Ceroba apologizes to Clover for attacking them, stating that spending time with them helped her forget her troubles. Clover cuts her off by walking up and hugging her.

With any obstacles now clear, Martlet prepares to take Clover to Asgore and the barrier, but Ceroba shoots it down, stating that Asgore would take their SOUL. Martlet, Starlo, and Ceroba all argue as Clover thinks to themselves. Remembering that monsters have suffered while trapped in the mountain, Clover ultimately decides to offer up their own SOUL so that one day, monsters can be free.

Despite Martlet and Starlo's attempt to convince them otherwise, Ceroba accepts their choice and agrees to take their SOUL.
The four then share one final hug before Martlet and Starlo leave, with Clover giving them their hat and gun respectively as a farewell present. Ceroba takes their SOUL and Clover sends her off before collapsing.

Flowey is then heard, expressing his disappointment at Clover becoming "predictable" by sacrificing themselves before stating that while he could RESET everything, he believes that Clover has earned their rest. He holds out hope that a future human would give him what he wants. Flowey then says his farewells to Clover before leaving, stating that they'll meet again (likely a reference to Flowey's plans to take the human souls). Clover then crawls up the side of the wall to pass away peacefully.

As the credits roll, the fates of many characters, both major and minor, are shown playing out. It shows:

Martlet, Starlo, and Ceroba walking to give Asgore Clover's SOUL.
Toriel walking by her tree in the Ruins as its last leaf falls off.
Dalv performing on his organ for an audience in Honeydew Resort.
Mo's business venture, depending on how many items were bought from him.
If 0-3 items were bought, Mo's business is a failure and he sits by himself with a coffee in hand.
If 4-8 items were bought, Mo's business is successful, with people lining up to purchase his popsicles.
If all nine items were bought, Mo's business becomes incredibly popular and he gets the Shufflers to work for him.
Slurpy's fate, depending if his side quest was completed or not.
If not completed, the Red Miner tries to pull off Slurpy from the pole but fails, to Slurpy's misery.
If completed, Slurpy is seen swimming in Honeydew Resort's hot springs.
Bryan's fate, depending on if his hardhat was returned or not.
If the hardhat was not returned, the mine workers mess around with minecarts while Bryan stands to the side and sheds a tear.
If the hardhat was returned, then Bryan gets promoted to being the new foreman and their fellow mine workers applaud.
Violetta with Rock Man, tending to the Oasis Valley sprout. After it suddenly blooms, Violetta and Rock Man share a laugh.

The Wild East being delivered corn thanks to the Feisty Five and Starlo's parents, with Starlo having accepted his farmer background again.
Guardener still hibernating, with Lil Bots 1 and 3 leaving the Greenhouse.
Axis on a date with Daisy in the Steamworks riding a gondola, with Sousborg rowing.
Ceroba knocking on the door of Dalv's new house while holding corn she bought from the Wild East.

In Waterfall, Martlet is seen preparing a small raft to send Clover off properly, before placing Clover's hat in the raft. As she does so, she reveals she declined a promotion and quit the Royal Guard for more important matters. Ceroba and Starlo arrive. Starlo puts Clover's gun in the raft and Ceroba then reveals that she invited Dalv to join the event. Starlo adds the Safety Glasses on the raft as well before Martlet places the raft in the water and sets it off, everyone saying their farewells to Clover. The Special Thanks credits play to the boat sailing down the river. After the last set of credits roll, the raft falls into the Garbage Dump, with the hat and gun landing on a patch of golden flowers.

Flawed Pacifist route:

The Flawed Pacifist Ending (also known as the Asgore ending) is reached by selecting the Fight option at the end of the final battle against Ceroba. She thanks Clover for freeing her of her guilt, happy to be reunited with Chujin again. Upon doing this, Clover kills Ceroba, leaving behind Kanako's shattered mask. Once Starlo and Martlet awaken to witness the scene, Starlo becomes furious and lashes out at Clover for killing his best friend, while Martlet defends them, stating that Clover's actions were justified since Ceroba was unreasonable and violent. Starlo disregards the idea of justice and, carrying Kanako's shattered mask, silently leaves New Home.

Martlet guides Clover to Asgore's throne room, presenting Clover to him, which momentarily shocks the king.

Martlet guides Clover to Asgore's throne room, presenting Clover to him, which momentarily shocks the king. Martlet attempts to reason with Asgore, but he is undeterred and reaffirms his no-tolerance policy towards humans, saying that Clover is not any different from the others. Martlet is devastated by the turn of events and asks Clover to defend their case, but Clover accepts the fate that stands before them and quietly indicates that Martlet should be on her way.

After Martlet leaves in sadness, Asgore brings Clover to the Barrier and reveals his five collected human SOULs. Clover briefly looks at them and then draws their revolver. Briefly, Asgore gives his sympathies to the child, saying he is well aware of the feelings they are experiencing. He promises he will make the fight quick before initiating a battle.

This battle is different from the standard encounter format of Undertale and Undertale Yellow: while there is a Bullet Board and a yellow SOUL that child can control, no other parts of the user interface are present, including Asgore's battle sprite. Attacks from Asgore keep coming in one never-ending wave, most being similar to the ones found in Undertale, but also including some that cannot be dodged. Clover never gets their turn and Asgore's turn continues until them is killed, at which point one of the empty SOUL receptacles appears and envelops Clover's SOUL. The receptacle joins the five others, and Asgore apologizes to the human one last time before the credits roll.

Post credits, Flowey is seen talking to himself, and decides not to RESET things, instead opting to wait for the next human to fall so that his plans can come to fruition.

Main protagonist of Undertale Yellow.
They are the sixth SOUL that is collected by Asgore Dreemurr in the Pacifist endings and the seventh human to fall into the Underground including Undertale's first human. Jumping into the Underground in search of justice for the previous five humans, they venture through old and new locations to reach the Surface.

Clover is an androgynous human child. They have short brown hair with a tuft in the back, as well as pale skin and a usually neutral expression. They wear a dark brown leather vest over a brown shirt and a pair of cuffed blue jeans. They wear a yellow and blue bandana, usually depicted as yellow with a blue polka dot pattern in official artwork, a pair of brown shoes, and a brown cowboy hat. Most of their artwork depicts them with a belt. During the Genocide Route, their eyes are hidden beneath a shadow. Some old official art depicts them with yellow irises.

While Clover is largely a silent protagonist, elements of their personality are shown or implied at several points. Generally, Clover has a strong sense of justice and a drive to do what they perceive to be the right thing, with some variations depending on the route. They have an affinity for unusual food and often steal without questioning. Despite their mission to reach New Home making up most of the story, in all of the timelines without Flowey's interference, Clover gives up their mission to live a peaceful life with Toriel, and during the Neutral Route, they never turn down Martlet's offer to live with her. Clover is referred to with they/them pronouns throughout the game because their gender is open for interpretation

In the final bosses in each route, Clover gains the ability to dash through attacks. Clover also gains the power to fire attacks of their own during the enemy turn.

Clover's SOUL bullets are most powerful in the Genocide Route, as their charged shots become a massive laser able to kill Asgore, destroy the throne behind him, and leave a massive hole in the wall of the room, all in one shot.

Also seen in the Pacifist and Genocide fights, Clover has the ability to reach out and access monsters' memories. This allows them to see the truth of situations and allows them to better carry out judgment. [citation needed] They use this in Ceroba's battle in the Pacifist Route each time they damage part of her mask, accessing her darkest memories and learning the truth behind her motivation for obtaining their SOUL.
In the Genocide Route, they use this ability against Zenith Martlet, scanning her memories for a reason to hate her and presumably also a justified reason to kill her. While this does not exactly appear in the Neutral Route, Clover invades Flowey's subconscious after the first phase and sees his uncountable amount of deaths, rendering a similar effect.

Clover's background is left vague. While never explicitly stated, it is implied that Clover may have come from an abusive or neglectful home because cramped living conditions bring unpleasant memories to Clover's mind. This may have resulted in them becoming independent at a young age. Interacting with plates in Ceroba's house reminds Clover of their duties back home, suggesting they were tasked with either washing the dishes or cooking. Sousborg compliments Clover's talent in cooking. Additionally, Clover seems against the idea of doing dishes without being told.

The most explicit detail is that their main reason for jumping into the Underground was to seek justice for the five humans preceding them. Because Flowey wants them to fight Asgore for him, he has been repeatedly resetting his SAVE and manipulating Clover for some time before the game takes place. After falling into the Underground, Clover originally chose to stay in the Ruins with Toriel.

Flowey is a character from Undertale that reappears in Undertale Yellow. He is a major supporting character throughout all three routes and the main tritagonist, appearing regularly to give his commentary on recent events and SAVE the game. Similar to Undertale, Flowey is the final boss of the Neutral Route.

Flowey's appearance is unchanged in Undertale Yellow. He is a sentient golden flower. He has six yellow petals, a white androecium with a face, and a light-green stem. He can change his face's appearance to make a variety of unusual facial expressions, which he usually uses to make disturbing faces.

Flowey, unlike in Undertale, acts friendly and helpful towards Clover. He follows them throughout the whole game. As Clover does not have enough determination to SAVE like Frisk, Flowey controls the SAVE file and SAVEs the game for Clover.

Flowey's true motives are the same as Undertale's: to acquire the human SOULs from Asgore and become powerful so he can have fun. Flowey attempts to subtly manipulate Clover over the course of the whole game to reach Asgore, as he believes this is the only way to steal the SOULs. He does this in various ways, including berating the other main characters to stop Clover from trusting them and reassuring Clover that he is trustworthy and their best friend. As established in Undertale, Flowey, having no SOUL, cannot feel love or compassion. When not acting, Flowey is violent, impatient, and typically emotionally numb; he is also childish, though that is not highlighted much in Undertale Yellow.

At the end of each route, Flowey expresses different opinions towards Clover. In the Neutral Route, Flowey says he held hope that Clover would entertain him, but they often fail to deliver, and he does not truly care about them. In the Pacifist Route, he calls them predictable, but says he will let them rest and calls them a friend.

In the Genocide Route, he claims that he always hated them and gets immense satisfaction from watching them repeatedly die, but is clearly attempting to get under their skin in their moment.

As explained in Undertale, Flowey is Asriel, brought back to life without a SOUL due to Alphys's experiments. He has had control over the timeline for a long time, growing more detached and bored as he continued resetting. He wants to obtain the human SOULs that Asgore has, but cannot get him to bring them out.

Flowey spent many resets trying to get Clover to confront Asgore in hope that this would let him access to the SOULs. In every timeline, when left alone, Clover always chose to stay with Toriel, so he drove tensions to rise until they confronted her and left. Past Toriel, though, they would always die before reaching Asgore. Flowey decided to tamper with the lever puzzle every time so it would send Clover into the Dark Ruins instead in hopes that this would change the ending.

Dalv is a humanoid vampire monster with fangs and horns. He has a lavender complexion and short, dark purple hair. For much of the Dark Ruins, he wears a maroon cloak with dark purple trim and a hood concealing his face. During his hangout, he takes off his cloak to reveal that he wears a white shirt underneath, with ruffles down the middle and a jabot around his neck.

In Pacifist Route Clover can find him in Snowdin wearing a large winter coat, maroon with white puffy trim around the ends. He also wears black gloves and smaller shoes.

Dalv is socially awkward and claims to desire solitude. He often talks to himself in long monologues or when talking to his household objects. Despite his reservations, he is convinced that staying in the Dark Ruins is the only choice for him and has completely shut himself away from the Underground and the Dark Ruins' other residents. On a Genocide Route, he laments how the Dark Ruins residents were similar to his friends and regrets pushing them away. Despite his anxiety, he has a backbone, standing up to Clover when mistaking them for Integrity and acting more firm if Clover attacks him as well. When hanging out with Clover, he seems very happy to have a friend to talk to and rambles to them. He has various creative hobbies, such as writing and illustrating children's books and playing the organ. He also enjoys growing corn.

While it is never stated directly, it can be inferred that, years prior to Clover entering the Underground, Dalv was friends with Kanako, and she was in Snowdin with Dalv when they were attacked by Integrity during an event that Chujin refers to as the Snowdin attack.

Though Kanako was unharmed, Dalv was injured.[5] From how Chujin refers to Dalv in the tape in a non-descript manner, it is likely that Chujin and Dalv never met prior to the incident. Additionally, it can be inferred that Dalv is aware of the death of the human in question.

After the incident, Dalv moved to live in the Dark Ruins in self-imposed isolation. Chujin began leaving cobs of corn at his doorstep every morning. While Dalv does not know who was leaving the corn, he considers them a friend and thinks of them often. After Chujin died, about a year before Clover enters the Underground, Dalv closed off the door to Snowdin.

Martlet is the deuteragonist of Undertale Yellow, the boss of Snowdin, and the main antagonist and final boss of the Genocide Route as Zenith Martlet. She is a member of the Royal Guard Snowdin Division.

Martlet is an anthropomorphic blue bird monster with a pale blue face and a small yellow beak. She has two feathery blue wings in place of arms and a large tuft of darker blue feathers around her neck. She wears yellow boots with a puffy trim. Her shoulder-length hair is the same blue as her wings with outsticking parts and a tuft at the back. She wears a pale blue sleeveless shirt, the same color as her facial feathers, and dark blue pants, the same color as her neck feathers.

Martlet is shown to be, as the game states, scatterbrained. She is forgetful, rambly, and often falls asleep at her station. She seems to struggle with concentrating on her duties and often relies on her manual for guidance. She has a passion for puzzlemaking and carpentry.

Martlet has a strong sense of morals and justice. However, she shows indecisiveness and a lack of confidence in her decisions, causing her to make the wrong choices in the moment and hindering her ability to deliver judgement. Despite this, she is persistent in trying her best, doggedly hunting down Clover when she loses them in all routes, although for different reasons. She also is optimistic to the point of appearing naïve. On the Pacifist Route, she is oblivious to the fact that taking Clover to Asgore would result in their death. At the end of a Neutral Route, her optimistic hope and sense of justice lead her to conclude that her best course of action is to take Clover in as a roommate, no matter how many monsters they have killed.

While this may appear foolish, not only does this go against the fear of humanity ingrained in her by monster society and Chujin's paranoia, Martlet's belief that Clover will not hurt her is entirely accurate, as even on an aborted Genocide Route her offer causes them to agree to end their rampage.

This also shows the nuanced sense of justice that she holds. Martlet goes as far as to defend Clover's decision to kill in the Flawed Pacifist Ending.

Martlet's optimism is broken throughout the Genocide Route as she tries to convince Clover to end their rampage, only to be defeated and ignored. She acts more serious; she retreats from her Snowdin battle upon realizing she cannot win and monitors Clover for the rest of their journey. At the end, her hope in humanity despite monsterkind's anger towards them is destroyed, and she risks her life by injecting herself with experimental determination to give her a chance at stopping Clover.

When she was in school, Martlet says a B- was an impressive grade. She also seemed to enjoy reading.

When she moved out to live on her own, she had no job or hobbies to keep her occupied. She met Chujin when he built her balcony and asked him to teach her to build. He agreed to mentor her. Martlet found enjoyment in construction and became good friends with him, meeting with him every morning and buying him coffee. Eventually, Martlet decided to get a job as well. She signed up for the Royal Guard and was assigned to guard Alphys's lab. Chujin reacted negatively when he heard the news, not wanting her to get hurt by any humans. Because of this, she broke into the lab to steal a vial of determination sometime before Alphys began injecting monsters.

Martlet was reassigned to the Snowdin Royal Guard Division by the time the game begins. She briefly mentions a vague risk she recently took that she regretted, but does not share details.

Starlo, known by his alias North Star, is the boss of the Dunes. He is the sheriff of the town in the Wild East, the leader of the Feisty Five, and the childhood friend of Ceroba.

Starlo is a humanoid monster. His skin is yellow with star-like appendages on his head with light blue patterns on them. He wears a brown poncho with light blue stripes with his sheriff badge on it, brown pants, and black boots with spurs. Starlo has a hat with teal highlights; all members of the Feisty Five have hats and teal highlights in their designs. Starlo carries a gun with him, which is actually a toy His overworld sprite usually has a smile, but in serious situations he does not have one.

Starlo's true personality is superseded most of the time by a Western persona. Borne out of a fanaticism of Wild Western culture, Starlo puts on this persona from a desire to spread excitement and drama to the inhabitants of the Underground, distracting them from the cruel reality of monsterkind's collective banishment from the Surface. Going by the moniker of "North Star," he plays the role of the Wild East's upbeat sheriff, who is determined to "keep the peace" by any means necessary. This for the most part is all drama, as there is no real danger (besides potentially Clover) and is all put on as a fun distraction for the Wild East's inhabitants, who all mostly seem to play along. While he touts the idea of justice, he uses it as an aesthetic and does not care for deeper moral conundrums, whether disregarding them or only seeing his own perspective.

Starlo values validation from others. He focuses on making spectacles to entertain the townsfolk and enjoys their attention. This is also the reason he eventually attacks Clover: to be revered by the entire Underground.

Starlo's true personality is revealed after his boss fight in the Pacifist Route. He is shown to be much more of a nerd - a picture in his home revealing he was even adorned with stereotypical dweeb braces at one point.

His room is filled with various Western memorabilia from the Surface. Despite this, however, one thing that is constant between "North Star" and Starlo is his kindness and how he values those close to him. In fact, this is the whole reason the "North Star" persona exists in the first place.

Starlo has been friends with Ceroba since they were young children. Starlo used to have a crush on her. When she got engaged to Chujin, he was so devastated that he did not leave the house for days. He has also been friends with the other members of the Feisty Four since high school.

Starlo found western tapes in Waterfall and loved them. He created the Wild East to entertain monsters with a western fantasy. He moved out of his house in the Sunnyside Farm to live with the Feisty Four in the same house.

After Kanako fell down, Starlo let Ceroba live in his house and take his bed.

The Feisty Four are a set of minibosses encountered in the Wild East. Alongside their leader, North Star, they form the Feisty Five (Fearlessness, Excellence, Intuition, Sneakiness, Toughness, Youthfulness, and Justice. The J is silent), a gang who rules the town. The gang members, aside from North Star, are Ed, Moray, Ace and Mooch.

Ceroba Ketsukane is a major character in Undertale Yellow. She is Starlo's best friend, Chujin's widow, and Kanako's mother. Intent on taking Clover's SOUL in order to complete Chujin's legacy and protect monsterkind's future, she serves as the final boss of the Pacifist Route.

During the Genocide Route, she replaces Starlo as the Dunes's boss, seeking revenge after Clover duels and kills Starlo.

In Ceroba's Pacifist fight, she puts on Kanako's mask, a white fox mask with pink markings, and drastically changes her appearance. She wears a cape over her dress. Her bow has three bells instead of one and is much larger. Her hair grows to resemble ten fox tails with pink tips.

Ceroba is a fox-like monster with beige fur. She has long, wavy ginger hair up in a ponytail tied by the Founder's Crest: a red bow with a small gold bell in the center. She has a short white dress, the top of which resembles a kimono, with red trim. She wears a red obi sash tied around her waist and white boots with red trim. Unlike Chujin and Kanako, she does not have a tail. Ceroba's design is inspired by the kitsune, trickster fox spirits from Japanese folklore, correlating with her attempt to trick Clover and take their SOUL. Ceroba is the tallest character in the main cast.

In battle, she wields a brown staff which again has the Founder's Crest, a bright yellow bell in the center of a red bow.

Ceroba appears skeptical and somber upon first meeting her. She acts as a straight man in much of the Wild East's antics, yet still makes the occasional sarcastic joke. She almost never cries; even Chujin only saw her cry twice in the time they were married. She is observant, able to read Clover without them speaking. She also has the ability to tell if their SOUL is pure or not, as even in their first conversation, her dialogue changes on a Neutral Route versus a Pacifist Route. She has an outlook that she considers mature.

At times, this makes her views more accurate, as she is the only one of Clover's friends who points out that Asgore will kill Clover if they go to New Home; on the other hand, she also holds unrealistic opinions she considers hard truths, such as being convinced that humans will force monsters back Underground once they reach the Surface. She considers Starlo to have not grown up like she did, but expresses some envy over how happy he is.

Ceroba is immensely devoted to her loved ones and to Monsterkind. Her devotion turns harmful at times, as she was willing to endanger her daughter and kill Clover for a possibility of fulfilling Chujin's legacy and protecting Monsterkind. She also turns a blind eye to Chujin's negative traits; she always holds him in high regard no matter what information is displayed to her that may say otherwise. She is firm on his legacy as a scientist and a hero of the underground, and she spends the time after his passing trying to complete the work that he had passed down to her.

Despite being observant and calling out others on their beliefs, Ceroba has a habit of hiding her issues and avoiding communication. She does not speak up about Starlo's behavior until after the Feisty Four already called him out on how it was making them feel. Nobody outside of her close circle knows about Kanako falling down, and she avoids sharing further information on it. This manifested strongly in her relationship with Chujin. They had poor communication; beyond Chujin keeping secrets their whole relationship, such as including a secret study in their house and experimenting on himself later, Ceroba and Chujin are implied to not have discussed basic plans for their relationship, such as how many children they wanted. She also lied to and manipulated Clover and Starlo in an attempt to get the former's SOUL, though she is not always good at lying.

Ceroba grew up in the mountains (presumably in or near the Dunes.) She was childhood friends with Starlo. He had a crush on her, and she once considered getting in a relationship with him.

She first met Chujin when she fell into a ditch. She twisted her ankle but considered ruining the crops her mother sent her to get to be worse. Chujin found her after some time and helped her out. While she describes this as sweet later, a flashback during her boss battle reveals she was driven to tears in the moment, something that Chujin never saw again from her until he was on his deathbed. Despite her commitment to family, this is the only time her parents are mentioned in the game.

They later got married and Chujin built the Estate to raise their family in, though they only ever had Kanako. Ceroba was a housewife while Chujin worked at the Steamworks. After he got fired, he claimed to have retired. He volunteered in Snowdin after this. Their family was financially struggling from the cost of building the estate at this point, so Ceroba had to get a job at Café Dune to support them.

Ceroba did not have much of a life outside of her family. She used to have a gym membership, was acquaintances with Martlet, and would bring Kanako to the Wild East on occasion.

Ceroba took care of Chujin as he became sick. He revealed his underground study to her on his deathbed. He died about a year before the game began. After his death, she spent months trying to figure out how to complete his serum without a pure human SOUL. While she eventually came up with a way to, in theory, remove the impurities from an extract from the Integrity SOUL, she still had no Boss Monster to test it on. When Kanako watched Chujin's tapes, she requested Ceroba use the extract on her to make the serum. This failed, causing Kanako to fall down. Ceroba sent her to the True Lab, something she later regrets as Alphys goes silent on updates.

Some time after Kanako fell down, and weeks before the game begins, Ceroba moved out of the Estate and into the Feisty Five's house in the Wild East. She sleeps on the bed, while Starlo takes the couch. She is implied to abuse alcohol during this time.

Chujin is Ceroba's late husband. Ceroba took care of Kanako and the Estate while Chujin worked at the Steamworks. After he claimed to have retired after he was fired, Ceroba also picked up a job at Café Dune to support their family as Chujin did volunteer work in Snowdin.

It is shown throughout the Pacifist Route that Ceroba loves Chujin very dearly and is devoted to him. Her devotion is to an extreme. She tries to avoid considering him in any negative light. For example, in the Steamworks, Ceroba shows resentment towards Asgore because of his criticism of Axis despite his criticism being fair and expresses pride over Chujin's award despite it being for his subpar work. She does not mention much of her life outside Chujin and Kanako, and the Estate does not show anything of her life outside them either– in fact, the only part of her house identifiable as hers is her clothes and the Corn Chowder.

Chujin and Ceroba had poor communication. Ceroba and Chujin never discussed Chujin’s work. Chujin directly lied about being fired, claiming that he had retired. He states in his tapes that this was so Ceroba would not think less of him. Ceroba was fully unaware of Chujin's experiments on himself and the Integrity SOUL until he was forced to tell her in an attempt to have her continue his project after his death. Ceroba and Chujin were even implied to not have discussed basic plans for their relationship, such as how many children they wanted.

Ceroba is confident that she has to continue Chujin's legacy, even if it means ruining her own life.

Kanako is Ceroba's daughter. As Ceroba was a housewife, she likely was around Kanako a lot. Ceroba is shown to deeply care about Kanako through dialogue and flashbacks.

Before Kanako fell down, the two of them had a routine every night where they would express their love for each other. Kanako also made a mask for her, which Ceroba later uses to transform into her final boss form.

Almost a year after Chujin's death and a few weeks after Clover enters the Underground, Kanako watched the tapes in Chujin's study. Kanako asked Ceroba to use the extract on her to make the serum, trusting that she successfully purified it. While Ceroba was initially reluctant to make Kanako a part of Chujin's plans, Kanako convinced Ceroba to use her SOUL. Kanako fell down soon after Ceroba gave her the extract. This sent Ceroba into a depression, the main cause of her moving out weeks before the game begins and of her drinking.

Axis Model 014, usually referred to as Axis, is the boss of the Steamworks. He is the final model of Chujin's failed line of robots built to eventually go to war against humanity. As it stands, he protects only the Steamworks.

Axis is a robot built with gray metal. He has a large box-shaped head with two pink, unevenly sized eyes and a horizontal line of four bolts or holes resembling a mouth on the front. His head has vertical antennae tipped with a small round light on each side and a large lightbulb and a curled exhaust pipe on the top. He has a round torso with a black heart symbol in the direction of a human SOUL on his chest with four bolts or holes surrounding it. He has another four bolts or holes in the same arrangement on the back, as well as a light yellow gear attached behind him on his right side. He has exhaust pipes sticking out sideways from each shoulder and light yellow gloves hovering independently of his body; his shoulder pipes emit smoke clouds that float into his wrists, implying a connection. He has a single leg with a wheel on the bottom.

Axis is able to change the shape of his eyes to express his emotions, which is only seen in the cutscene after sparing him on the Pacifist Route. He says he blushes a bright gray in the Neutral Route but is seen blushing pink during the Pacifist Route credits.

In genocide, after being shot by Clover at the beginning of the route in the Steamworks, Axis is permanently damaged. His left eye is shattered and the casing around it is removed. His right hand loses several digits. His left antenna is damaged and its lightbulb is missing. Additionally, the lightbulb on the center of his head cracks and no longer emits light.

Axis is programmed to be dedicated to the security of the Steamworks. Once he catches sight of an intruder, he becomes single-minded in his pursuit of them.

Despite his physical agility, his effectiveness as a guard is greatly hampered by his gullibility and slow wit.

He inadvertently allows Clover and Ceroba to escape his capture several times and easily falls for obvious tricks. In the Genocide Route, Axis becomes less clumsy and far more serious, evading Clover's pursuit all throughout the Steamworks.

Beneath his unsophisticated surface, Axis is a sapient being shown to experience complex emotions. He is short-tempered, passionate, and sometimes egotistical. He is quite foul-mouthed, though a profanity filter censors his cursing due to the fact that, although Axis is the only bot that tries, all robots are forbidden from cursing. Axis greatly misses Chujin due to Chujin's kindness. Axis is also capable of experiencing loneliness and romantic love; after he mentions he is lonely, Clover and Ceroba built a companion robot to distract him with, which he becomes besotted with, declaring them his spouse.
In the Genocide Route, Axis expresses remorse over killing the previous fallen human and helps protect the Steamworks bots at risk to himself. He expresses fear towards Clover and remorse for Clover's actions, as he blames himself for their rampage.

Axis, being a robot, has several restrictions. He cannot go against his programming, even when it causes him distress. After a recharge, he is reset to his "factory state" and has to scan people to remember them.
This is made irrelevant after introducing him to Daisy, as he can then function on love alone and no longer needs to recharge. After Clover knocks him out of his programmed fixation on capturing them, he regrets his previous actions, behaves far more calmly and friendly towards them, and, despite the fact that they are still an intruder, grants them permission to enter the Steamworks.

Axis was created by Chujin when he worked at the Steamworks. He was pitched as a guard bot, though the final goal of the AXIS project was to go beyond simple security and use them go to war against humanity.

Unlike other bots in the Steamworks, who are part of some sort of hivemind, Axis does not operate under this control.

Chujin presented many failed prototypes to Asgore, which self-destructed in various humiliating ways. When showing Model 08 to Asgore, it malfunctioned. Sparks flew from the machine, setting a patch of Asgore's flowerbed ablaze. Though the fire was quickly put out, Asgore told Chujin to not return.

While Chujin was still working on Axis, Integrity arrived in the Underground. They got into a fight with Dalv, who was playing with Kanako at the time, before fleeing to Waterfall. Chujin felt it was his responsibility to order Axis to hunt down this human, prioritizing giving this order over comforting Kanako. Axis was swift to get the job done, immediately making his way to Waterfall. He then killed the human due to an error in his programming. This is indicated within the Genocide Route to be something that Axis did not willingly carry out. Chujin took the human SOUL for experimentation and told Axis to hide the evidence. Axis was returned to the Steamworks. His memory was wiped of the attack and Chujin expressed a desire to keep improving on him.

Various robot parts from earlier Axis models are found in Chujin's study. This could possibly insinuate that Asgore's dismissal was Chujin's firing and he continued working on Axis past Model 08 in his home in secret. However, his firing may also have been some time after this incident, since Chujin expresses finality in the tape where he discusses his firing, possibly implying that he gave up on the Axis project because of his firing, and it is unknown how Axis Model 014 would be registered in Vendy's systems if he was not built in the Steamworks.

A while after Chujin was fired, the Steamworks shut down and were replaced by the CORE, so Axis was powered down for a long time. The other iterations of Axis have ceased to function by the time Clover enters the Steamworks.