Guilt gets a bad reputation. We treat it as something to move past, and eventually discard. It’s treated as an inconvenience at best. In Chainsaw Man, the series argues that guilt might be the most powerful force in existence.
To know why, you need to understand Asa Mitaka and her complicated relationship with the War Devil.
Asa’s Contract With the War Devil
Asa is introduced in Part 2 of the Manga as a socially awkward student at Fourth East High School. She accidentally causes the death of her class’s pet devil, a small, harmless creature named Bucky. The fallout is brutal as she becomes an outcast.
Then, in a brutal twist, her class president murders her out of jealousy. As Asa dies, she is greeted by Yoru, the War Devil. One of the four Horsemen who embodies the concept of war. Yoru offers to resurrect Asa in exchange for her body. Asa accepts and becomes a living Fiend host. Asa retains her human personality (until Yoru takes control of her) with half her brain left intact while the other half is inhabited by the War Devil.
Everything that follows is a direct consequence of that fateful meeting.
What Yoru Wants From Asa
Yoru’s plan is to use Asa’s body to hunt down and kill Pochita (the Chainsaw Devil). Pochita had eaten parts of her in the past and she wants to restore her former glory. She sees Asa as a means to get to Denji, who has merged with Pochita, and keeps threatening to seize full control. But her real interest in Asa is in her emotions.
Yoru’s power can transform anything she considers to be her property into weapons. A jacket becomes a sword. A person she’s bonded with becomes a spear. The weapon’s strength is proportional to her guilt or attachment. Her power scales with human’s fear of war, allowing her to turn people, objects, and even other devils into weapons. And the feeling she needs most is guilt.
The Confession That Changes Everything
In chapters 229 and 230, Asa and Yoru are both bleeding out after their brutal fight with Denji. And Yoru, an entity who exists to weaponize human suffering, admits something surprising.
She once possessed a bird. Even then, small as it was, she felt the bird’s guilt for catching and eating worms. She embraced that guilt and it made her stronger.
After merging with Asa, Yoru tried to understand her guilt. The guilt she had over Bucky, every person she hurt, compromises she made just to survive. But Yoru could never truly understand Asa’s human emotions or her guilt.
The reveal paints their dynamic in a different light. Yoru has been keeping Asa alive because she cannot replicate her ability to feel certain emotions. Fear, hatred, rage…those feelings come naturally to a devil. They require no conscience, no sense of how things should have gone differently. But guilt does. Guilt is the shame and remorse we feel from doing something wrong. The mind is haunted by what has happened, and what we could have done better.
It’s something Yoru cannot generate on her own. So she borrowed it.
The Irony of the War Devil
The War Devil’s goal is to plunge humanity into an endless World War II (Chainsaw Man takes place in an alternate universe where many life-altering events never happened). Yoru exists to make people suffer under a perpetual cycle of destruction where she can always pray on their fear. And yet the weapon she needs most, the one that makes her so dangerous, is forged from remorse itself.
She is dependent on a concept that would make it impossible for her to achieve her goal.
What makes Asa so compelling is that she and Yoru represent how the same emotion can manifest itself. Asa is paralyzed by guilt. Bucky’s death wasn’t her fault, but it still haunts her in a sense. The remorse she feels every time a person has been hurt or killed due to Yoru using her body accumulates. Yoru dismisses these feelings as trivial, that she considers these sins to be insignificant in a devil’s eyes. From Yoru’s perspective, Asa’s guilt is disproportionate to the actual damage done.
But Yoru is incapable of feeling guilt. She can recognize it, sort of like the way you might recognize a smell you can’t quite name. Even after sharing a brain with Asa, Yoru is still incapable of understanding what it feels like to believe you should have done better.
What This Says About Their Relationship
Yoru and Asa are not just a devil and its host. They are, in a strange way, incomplete versions of the same thing.
Asa has the emotional depth that makes Yoru’s weapons powerful. Yoru has the strength and survival instinct that keeps Asa alive. They need each other in ways neither of them fully acknowledges.
That gap is what fuels their relationship. It’s why, when Yoru crashes her motorcycle to avoid killing a dove, breaking her own momentum because Asa’s compassion has seeped into her against her will, it feels like the most human thing the War Devil has ever done.
