Transfer

The Quirk whose only power was to hand itself on.

The transferring half of One For All in My Hero Academia comes from a Quirk called Quirk Bestowal. It belonged to Yoichi Shigaraki, the sickly younger twin brother of All For One, who was long believed to be Quirkless. Quirk Bestowal had a single ability: it could transfer itself to another person through the holder's DNA.

Lore & Background

All For One forced a power-stockpiling Quirk on his brother, and it merged with Quirk Bestowal. The result was One For All, a store of power that can be handed from one person to the next. After All For One killed Yoichi he found that the Quirk had already passed to Toshitsugu Kudo.

Reader's Guide

The handover works through DNA. Izuku Midoriya receives One For All by eating a strand of All Might's hair. In the final battle he uses the same property as a weapon, forcibly transferring One For All to Tomura Shigaraki in order to damage his soul. The vestiges also warn that One For All slowly kills a holder who already has a Quirk of their own.