Hardening (硬こう化か Kōka?): Eijiro's Quirk gives him the power to harden and sharpen any or all parts of his body, causing his flesh to become jagged and rock-like.

There is a limit to how much damage his hardened body can withstand, which causes the Hardening itself to slowly dissipate, and Eijiro to lose stamina from struggling to keep his Quirk active.[5] However, when he battled Kendo Rappa, Eijiro displayed the ability to refortify his hardened body.