Are nine Quirk Users who all at some point who all at one or currently hold the power of extremely powerful quirk called One For All a transferable quirk. With the current holder being Izuku Midoriya.
The Quirk began around the point when a man by the name of All For One who had a quirk that could steal others and also give them away. He gave his younger brother by force a quirk that allowed him to stockpile power within his body. However, unknown to them, the little brother already had a Quirk with no effect other than that it could be transferred to others. His Quirk and the Quirk his brother gave him merged to become One For All. He tried to defeat his brother but failed.
At some point in his life he transferred his Quirk to another person hoping that a future user would to defeat his brother.
For 7 generations each user had failed to defeat All For One however with each passing on the Quirk became stronger and stronger with each generation until reached it's 8th Holder Toshinori Yagi who used it t defeat All For One however knowing that a great evil will rise again to take his place he passed to the 9th and current Holder Izuku Midoriya.
One For All is transferrable by current holder, The method of inheritance and transference of One For All is done by the recipient ingesting the current wielder's DNA, as shown when All Might gave Izuku Midoriya a strand of his hair to ingest, which let the latter inherit One For All. The Quirk can not be stolen as requires the will of the owner to pass on however this does not mean One For All cannot be forcibly passed on.
The previous owner can still access remnants of embers of this power and thus still access its power. However, these leftover embers will not last for long, and the previous One For All will slowly lose their access over the Quirk, resulting in the predecessor losing One For All completely.
- All for One's brother(1st Holder)
- 4 unnamed holders
- Daigoro Banjo(5th Holder)
- Nana Shimura(7th Holder)
- Toshinori Yagi(8th Holder)
- Izuku Midoriya(9th Holder and Current Holder)
From has been seen so far most holders of One For All have been consider among the strongest Heroes of their generation. All members bar Izuku had fought even with All For One though none had been able to defeat until Toshinori Yagi came along and eventually defeated.