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. However, when he battled Kendo Rappa, Eijiro displayed the ability to refortify his hardened body.