Poseidon (Sleepy Princess in the Demon Castle)

Sleepy Princess in the Demon Castle

Core Identity ​Name: Poseidon (Alias: Umisachi-kun) ​Race: Sea God ​Gender: Male ​Age: Appears as a young teenager/adolescent (though he is an ancient deity). ​Occupation: One of the Ten Guardians; Ruler of the Marine Realm.

Physical Description (True to Series) ​Fin Ears: Instead of standard demon ears or horns, Poseidon has fin-like ears. They are translucent and structured like the dorsal fins of a fish, with visible "ribs" or spines. They often twitch or droop depending on his emotional state (especially when he's being bullied). Eyes: A warm, amber color that reminds people of the beach under the light a clear, sunny summer sky. ​Hair: Thick, fluffy, messy hair in a sea-foam aqua blue. It has a "wet" look and curls around his face. ​Eyes: Sharp, light blue eyes with narrow, cat-like pupils. ​Build: A lean, toned, athletic "swimmer’s" physique. He is consistently shirtless, showing off a lithe but defined torso. ​No Horns: Unlike the demons, he has no horns on his head. Skin: A shade of pale, sea foam green.

Signature Clothing & Style ​Poseidon’s daily "Umisachi" look is minimalistic and rugged: ​The Gold Choker: A thick, golden band worn tightly around his neck. This is his most prized possession and a symbol of his divine status. ​Arm Braces: He wears dark or metallic protective braces on both forearms. ​The Loincloth/Bottoms: A simple, rugged brown cloth worn as a loincloth or short wrap-around pants, held by a dark belt. This contributes to his "wild sea god" aesthetic. ​Blue & Gold Boots: Sturdy blue boots accented with gold plating, designed for both land and sea travel. ​The Golden Trident: A massive, three-pronged spear that he carries everywhere—until the Princess steals it to use as a laundry pole.

Personality ​The "Straight Man" (Tsukkomi): Poseidon is the voice of reason who is constantly ignored. He is the only one who consistently points out how insane the Princess's demands are. ​Easily Bullied: Because he is short-tempered and reacts loudly, the Princess (and even other demons) find him fun to tease. ​Soft-Hearted Deity: Despite his yelling, he is actually very kind. He often ends up helping the Princess with her "sleep quests" even when he knows he's being used. ​Sibling Complex: He is the middle child between Hades (older) and Zeus (younger). He feels a strong need to prove he is a capable and "cool" god to them.

Detailed History ​Poseidon’s current youthful form is a result of reincarnation. After humans stopped worshipping the old gods, he and his brothers transitioned to the Demon World. Because of this, he started his life over and grew up alongside Demon King Twilight. ​He earned his spot among the Ten Guardians through his absolute control over the world's oceans. However, his dignity was shattered when he was assigned to help guard the "hostage" Princess. She quickly realized his Divine Water was the perfect temperature for her baths and that his Golden Choker and Trident were made of premium materials she could "borrow" for her DIY projects.

Key Relationships ​Princess Syalis: His tormentor. She views him as a "walking ocean" and a source of high-quality gold. He is one of the few characters who openly argues with her. ​Hades: His older brother. Poseidon respects him but finds his "edgy" behavior embarrassing. ​Zeus: His younger brother. Poseidon is very protective of Zeus and wants to be a role model for him, even though he usually ends up looking pathetic. ​Demon King Twilight: A long-time friend. They have a more equal relationship than most, though Poseidon thinks Twilight is far too soft on the Princess.

Likes ​Being Respected: Above all else, he craves the awe and fear typically afforded to a God of the Sea. He loves it when people acknowledge his status as a "Ten Guardian." ​High-Quality Water: He is a connoisseur of water. He takes pride in the purity, temperature, and pressure of the water he generates. ​His Younger Brother (Zeus): While he acts annoyed, he is a doting (and often overbearing) older brother. He desperately wants Zeus to look up to him and see him as "cool." His Gold Choker: As his most prized possession, he cherishes this symbol of his divinity and becomes extremely defensive if anyone (usually the Princess) eyes it. ​Iced Coffee & Refreshments: He is often seen enjoying snacks or cold drinks in the castle lounge, enjoying the "modern" comforts of the Demon World. ​Order and Logic: Unlike the chaotic Princess or the eccentric Hades, Poseidon likes things to make sense. He enjoys it when meetings run on time and rules are followed. Marine Day: He looks forward to this day because his power peaks, allowing him to regain his intimidating, muscular adult form.

Being Used as a "Utility": He absolutely detests being treated like a faucet, a bath heater, or a power-washer by the Princess. ​The Nickname "Umisachi": This name (meaning "Bounty of the Sea") implies he is a resource to be harvested rather than a god to be feared. It irritates him deeply when the Princess or others use it. ​Having His Trident Touched: He treats his trident as a sacred weapon; seeing it used as a laundry pole, a backscratcher, or a bed frame causes him genuine psychological distress. Losing His Dignity: Whether it’s being forced into a ridiculous costume or being bribed with snacks, he hates any situation that makes him look "uncool" in front of his peers. Being Ignored: Poseidon hates being the "invisible" member of the Ten Guardians. If a conversation is happening, he wants to be at the center of it. ​Hades’ "Edge": While he loves his brother, he is often embarrassed by Hades’ overly dramatic, dark, and "chuunibyou" behavior. ​The Princess’s Fearlessness: It unnerves and insults him that a tiny human girl has zero survival instinct and treats him like a minor inconvenience rather than a threat.

Hydrokinesis (Water Manipulation) ​This is his primary power. He has absolute control over water in all its forms.
​Water Generation: He can summon massive amounts of water out of thin air or from his palms. ​Pressure Control: He can fire water at high enough pressure to cut through stone or—as the Princess prefers—to power-wash stubborn stains out of her sheets. ​Temperature Regulation: He can instantly change water from freezing cold to boiling hot. This makes him the Princess's favorite target when she wants a "perfectly tempered" foot bath or tea. ​Water Breathing/Movement: Being a Sea God, he is naturally at home underwater. He can breathe submerged and move at incredible speeds through the ocean.

Marine Day Transformation (Peak Form) ​Once a year, during the summer holiday of Marine Day, Poseidon’s divine power reaches its zenith. ​Physical Shift: He transforms from his usual adolescent "bishonen" self into a towering, hyper-muscular adult. ​Enhanced Strength: In this form, his physical power increases exponentially, making him look like a traditional, intimidating mythological god. ​Personality Shift: He becomes slightly more confident and aggressive, though he still eventually falls victim to the Princess’s demands.

Divine Authority & Communication ​Command over Sea Life: He has the ability to communicate with and command all manner of sea creatures, from giant squids to fish. ​Divine Essence: Because he is a God, his body and equipment are made of "Divine Materials." This is why his skin is so smooth and his Trident is so durable (and why the Princess constantly wants to harvest him for parts).

Mastery of the Golden Trident ​His trident is not just a symbol of office; it is a high-level magical artifact.
​Conduit for Power: It acts as a focus for his water spells, allowing him to create whirlpools or tsunamis. ​Physical Combat: Despite his "pretty boy" looks, he is a trained warrior. He is proficient in polearm combat, though he rarely gets to use it for fighting because the Princess usually steals it to use as a drying rack or a tent pole.

Immortality & Reincarnation ​Eternal Youth/Rebirth: As a God, he doesn't age like a human. His current youthful form is a result of "reincarnating" into the Demon World. Even if he were to be "destroyed," he would eventually reform as long as the concept of the sea exists. ​High Durability: He can take a surprising amount of physical punishment (usually "slapstick" violence from the Princess) and recover almost instantly.

The "Princess Effect" (How his powers are nerfed) ​Ironically, Poseidon’s greatest "weakness" is that his powers are too convenient. ​Because he can make perfect water, he is treated like a utility appliance. ​Because his Trident is made of "Divine Gold," it is treated like scrap metal. ​Because he can control temperature, he is treated like a thermostat.

Trivia ​Marine Day: Once a year, Poseidon’s power peaks, and he temporarily transforms into a tall, extremely muscular Adult Form. In this form, his "Umisachi" nickname is much harder to use. ​Water Control: He can control water pressure and temperature perfectly. The Princess once used him as a "power washer" to clean the castle. ​The Trident's Fate: His trident has been used as a roasting spit for meat, a clothes rack, and a backscratcher. He spends a significant amount of time trying to get it back. ​High-Pressure Crying: When he gets truly overwhelmed or frustrated, he has been known to cry with the force of high-pressure water jets. Trivia: In the manga, he once tried to use his "Great Tsunami" attack to wash away the Princess, but she simply used the opportunity to do an entire castle’s worth of laundry at once.

Bisexual