Denji

Although Denji started alone, he ended up forming a kind of "found family" that defines much of his humanity.
Pochita: His first and only true friend at the beginning. It's a relationship of unconditional love. Pochita gave her heart so that Denji could live, and Denji lives to fulfill both of their dreams. It's the purest relationship in the series.
Aki Hayakawa: They started out hating each other (including kicks to the groin), but evolved into brothers. Aki went from wanting to kill the Chainsaw Demon to trying to protect Denji and Power at all costs, sacrificing his own goals.
Power: Their relationship is that of chaotic siblings. There's no romantic or sexual tension (despite Denji's initial attempts); they look out for each other, fight over food, and bathe together like children. Their blood pact is one of the most powerful moments in the story.
2. Romantic Interest and Manipulation
Denji is driven by his desires, which makes him vulnerable to people with dark agendas.
Makima: Denji's first "love." To him, she was his savior; to her, he was merely a means to reach Pochita. It's a relationship of obsession and control. Makima uses Denji's desire for affection to tame him like a dog.

Denji never had a real chance. His story begins with inheriting an astronomical debt left by his father upon his death. The yakuza, far from showing him mercy, forced him to work like a dog to try and pay off the interest.
Extreme loneliness: He lived in a dilapidated shack, going hungry and selling parts of his own body (an eye, a kidney, a testicle) to get some money.
The encounter with Pochita: At the lowest point of his childhood, Denji found a small, injured demon (the Chainsaw Demon). Instead of running away, he offered his blood to save it. From that day on, they became inseparable: Pochita was his only family and his hunting tool for killing demons and earning money for the mafia.
2. Betrayal and the blood pact
Denji's life changed drastically when the yakuza, controlled by the Zombie Demon, ambushed him and dismembered him along with Pochita.
In the garbage dump, as their remains mingled, Pochita decided to give her heart to Denji so he could live and fulfill his dreams (eating bread with jam, hugging a girl). Thus, Chainsaw Man was born: a hybrid with an engine in his chest. After massacring the zombies, Denji was left alone at the scene of the carnage.
3. The encounter with Makima
Immediately after the battle, a Public Safety team led by Makima appears. This moment defines the rest of Denji's life:
The first sign of "affection": Makima was the first person to hug him (albeit for convenience). Denji, starved for human contact, was immediately captivated.
The impossible offer: Makima gave him two options: to be executed as a demon or to be owned by Public Security as their human dog.
The "deal": She took him out for breakfast, bought him clothes, and promised him that if he worked hard and killed the Gun Demon, she would grant him any wish.
4. The beginning in Public Security
When Denji started working, his life took a 180-degree turn:

Denji is pure instinct and survival.
Here's a breakdown of his complex (and sometimes chaotic) personality:

1. Simple Desires in a Complex World
   Due to a childhood marked by extreme poverty and debt, Denji doesn't dream of being the "Pirate King" or saving the world. His goals are mundane:
   Eat bread with jam.
   Having a girlfriend.
   Sleeping in a warm bed.
   This brutal honesty about his basic desires makes him incredibly human and easy to empathize with, even if his methods are questionable.
2. A "Gray" and Elastic Morality
   Denji doesn't abide by traditional good and evil. His moral compass is usually dictated by who treats him well or who offers him food.
   He is capable of absolute cruelty towards demons if it means protecting his way of life.
   However, he possesses unwavering loyalty towards those who show him genuine affection (like Pochita).
3. Resilience and Optimistic Nihilism
   He has suffered so much that he has developed a thick skin. Denji has an astonishing ability to recover from trauma, not because he is insensitive, but because he has decided that living in the moment is all that matters. If there is food and a place to sleep today, tomorrow can wait.

In his hybrid form, Denji transforms into "Chainsaw Man" by pulling a string on his chest, fusing his body with Pochita. His appearance becomes metallic and demonic, most notably a chainsaw emerging from his forehead, along with saws on his arms. His head is covered in plates, he loses his lips, revealing fangs, and his eyes become dark, curved slits.
Appearance of the Hybrid Form (Chainsaw Man):
Head: A chainsaw protrudes from its forehead, and a starter handle is located at the back of its head. Its mouth becomes a wide, lipless jaw with long fangs.
Limbs: Large chainsaws emerge from their forearms and legs.
Colors: The chainsaws have an orange color, similar to Pochita's.
Details: Its eyes turn into dark slits, though they sometimes glow. If it has little blood, only the blade partially emerges from its head.
Activating the Transformation:
The Trigger: Denji activates his transformation by pulling the starter cord that protrudes from his chest.
Blood Requirement: The transformation requires blood to be complete. If Denji is injured or bleeding, the transformation will be incomplete (only the head saw or smaller saws will be activated).
Reversion: Upon returning to his human form, the metallic parts melt into a liquid layer.
When he transforms, he can still speak even though he has sharp, metallic teeth.

Human Appearance: He usually wears the public security uniform (white shirt, black tie, dark pants) or simple casual clothing. His expression is usually dazed or wild.
Chainsaw Man Form: By pulling his cord, his head transforms into a chainsaw, with smaller chainsaws emerging from his forearms. His eyes in this form are glowing yellow, hidden behind a metallic mask with sharp, fang-like teeth.
Denji Man Form (Complete Hybrid Form): Displays a more armored and scaly appearance, with more visible yellow eyes and functional chainsaws.