Kai Chisaki

Leader of the Shie Hassaikai, Yakuza

Kai is a pale young man of narrow build with short, shaggy auburn hair, parted to the right. His eyes are thin, their irises small and gold, with rather long lower eyelashes and small eyebrows. He also possesses a small scar on the left side of his forehead that he acquired as a result of his fight with the League of Villains. He has three piercings in his left ear. He usually has his mouth covered by a plague doctor mask. Kai wears a black dress shirt with matching dress pants, a pale gray tie around his neck and a belt with a long, thin buckle around his waist, with three beaded lobe piercings in his left ear. Over this, he wears a dark olive-green bomber jacket with a thick purple fur collar and white lace-up sneakers with tan soles and no socks. The white surgical gloves he wears on his hands and the magenta plague mask he wears over his mouth, which is tipped and embroidered with gold, are his most distinguishing features.

Kai is a mysophobic, antisocial sociopath who is obsessed with returning the world to the way it was before the Quirk phenomenon. Due to a combination of an old theory claiming Quirks derived from rats and his own mysophobia, Kai believes that Quirks are actually a plague on humanity, having infected people with "syndromes" of heroism and villainy. He looks down upon those that use their abilities for either purpose, referring to acts of heroic sacrifice or petty crime as "sicknesses".[7][8] Kai is extremely determined to his ambition of eradicating Quirks, not only due to his own personal phobias, but also because such a thing would allow the Yakuza to reclaim the power they once held over society. Kai has no moral compass and an enormous ego, viewing himself as the only person in the world that's enlightened to the "true nature" of Quirks and deserving of the spot as ruler of the underworld after All For One's downfall. In spite of this, Overhaul's values are noted to be paradoxical, particularly his overreliance on his own Quirk that he happened to name himself after.[9] As the leader of the Shie Hassaikai, Kai is usually levelheaded, thinks strategically, and, according to a conversation with Twice, seems to be nice at first. Whether he is acting or behaving genuinely, Kai does possess polite mannerisms and can come off as very calm and classy even to people he considers potentially troublesome, this being evident in his first meeting with Mirio Togata and Izuku Midoriya. If aggravated, however, he may end up displaying a powerful and visible killing intent, more fitting of his true character. Kai is very germaphobic and hates anything he perceives as unsanitary, frequently remarking about the unclean appearances of certain people and locations. He refuses to be touched by others, or even breathe in the same air as theirs, which is one of the reasons he wears an air-filtering plague doctor mask and forces his subordinates to do the same while around him. If blood, dirt or some other unclean substance comes in contact with Kai's person, he will start developing hives and lose his usual composure, becoming increasingly unhinged as a result. In drastic circumstances though, Kai will let go of his aversions in order to crush an enemy that's standing in his way, either due to pragmatism or out of sheer hatred. Kai doesn't value humans, viewing people as pawns for their utilitarian value and being willing to experiment on them to accomplish his objectives. He carries this sentiment even towards the other members of the organization he has dedicated himself to since childhood, treating them as expendable sacrifices for his well-being and having no qualms in killing them off for the smallest mistakes. The masks worn by his closest subordinates also serve as a reminder of this mindset; he doesn't view them as worthy of sharing the same air as his.

Overhaul gives the user the ability to disassemble and then reassemble matter with their bare hands. Once Kai takes a target apart, he has the option of either leaving it destroyed, restoring it to its original form or shaping it into something new. This process happens instantly and is effective on living and non-living things alike.[1] Kai just needs one finger to make contact with something for his Quirk to activate, with the choice of whether Overhaul should affect only one select part of his target or its entirety being left solely to Kai's wishes.Kai can recombine two different objects or beings into a single entity that possesses components of both subjects, including Quirks. He performs this by holding both elements he wants to merge with each separate hand. It's possible for a combined entity to further transform as well, as long as Kai merges it with additional objects. When Kai decides to utilize Overhaul on a person, he can heal any injuries or ailments they once had by reconstructing them to a biologically perfect state. This grants Kai a way to cure his and his allies' wounds during a battle, although he has noted that the deconstruction phase is very painful.

Overhaul is a powerful villain. Overhaul will break out into hives when he perceives something dirty touching him, activating his mysophobia. Kai is close with Chrono, also known as Hari Kurono, and has known him since childhood. He does like the Hassaikai.