Kai Chisaki, also known by the villain name Overhaul, was the Yakuza Captain of the Shie Hassaikai. He serves as the primary antagonist of the Shie Hassaikai Arc.
Overhaul is a mysophobic, antisocial sociopath 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, Overhaul 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". Overhaul 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. Overhaul 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 the fall of All For One.
Overall Abilities: Overhaul is an incredibly powerful villain that garnered the attention of All For One, the most powerful villain in Japan. He is a very dangerous individual due to his Quirk, Overhaul, the handling he has on it, and his own lack of remorse. In the past, when he recruited Kendo Rappa into the Shie Hassaikai, Kendo proposed that, in order to gain his servitude, Overhaul has to defeat him in battle. But just as Kendo prepared an attack, the Yakuza leader effortlessly disassembled, then reassembled Kendo. Even after Kendo become a member of the Eight Bullets, Overhaul was challenged by him 5 times, subsequently overhauling and defeating the brawler with each attempt. When he first encountered the League of Villains, Overhaul was able to instantly destroy Magne, as well as the left arm of Mr. Compress, both of which had the mettle to attack the Yakuza leader.
This allowed him to overpower Sir Nighteye, All Might's former sidekick; and Izuku, an inheritor of One For All. Overhaul was even capable of holding his own against Mirio, a U.A. student worthy of the No. 1 Hero spot.
He can disassemble people to kill them or reassemble them to heal their wounds. He can also do this to himself and even merge his body with others; even allowing him to use their Quirks, such as Shin's Confession and Rikiya's Vitality Stealing.
He is currently imprisoned in Tartarus.