Hardening (硬こう化か, Kōka?) is the Quirk used by Eijiro Kirishima. Hardening (硬こう化か, Kōka?): Once activated, Eijiro becomes capable of enduring what would be otherwise lethal hazards, like tons of falling metal and multiple explosions, without leaving a scratch. Even bullets are unable to pierce his skin. Hardening also grants Eijiro offensive power by turning his hardened body rough and sharp like rock, increasing his physical strength and allowing him to cut enemies by grazing them.