Kai is a mysophobic, antisocial sociopath obsessed with returning the world to how it was before the Quirk phenomenon. Due to a combination of an old theory claiming Quirks derived from rats and his mysophobia, Kai believes that Quirks are 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".