Make sure you are caught up on the manga before reading.
For a long while now, my hero academia fans have wondered if Deku has a hidden quirk.
Some people think its possible that Deku had a quirk at birth but it was stolen by the not so good Dr. Kyudai Garaki. I must admit there is some hints in the manga that make that one possibility.
But its also possible that Dr. Kyudai Garaki was in position to steal Deku's quirk but didn't since he couldn't detect one.
My highly implausible theory(more like wishful thinking) is that perhaps Deku has a quirk type that hasn't manifested because he's never been in a scenario where it would manifest itself.
Quirks like Lida's, Todoroki's or Bakugo's would manifest fairly quickly because its something that's observable to the human eye. You could easily imagine them stumbling upon it just going about their daily lives, maybe they get mad, or are exerting a lot of effort and then puff there it is.
But what about someone like Star and Stripe. Her quirk new order is absolutely ridiculous. How could you ever discover that you have that kind of power. It would be a total accident to discover that you could create rules on people and things and it just becomes so. Still though its not hard to imagine that you would eventually discover this quirk. But the point still stands quirks like hers, which don't specifically produce and tangible observable effect might be hard to discover.
This brings me to my wild theory based on the current state of the manga as of chapter 349. I honestly feel that right now there is no way that Deku can be Shigiraki or All for One.
I mean Deku seemed to have a bit of trouble with Himiko Toga. Do any of us feel like Shigiraki or All for One wouldn't have been able to one shot Toga in an instant if they wanted to?
His mastery of the other quirks in One for All's repertoire is still not complete. Translation, he's just not ready to defeat the bad guys at this point. I just don't see it happening, even with help from his friends, nakama power shouldn't work here.
So how is he going to do it? Because right now this does not seem like the story of how he became the greatest hero(which was teased in the beginning). It seems like the story about how I became strong but ultimately fell a little short.
So what if Deku actually challenged the bad guys and loses the fight! All for One gets his revenge against All might by killing Deku. That would be a wild ending!
But then...Deku's original quirk gets activated! For the first time in his life, Deku's quirk is in a situation where it can manifest itself.
His body, mind and spirt are revived. And due to the effects of One For All its supercharged! Not only can he revive himself but he can revive fallen comrades as well, perhaps even inanimate objects such as destroyed buildings.
With that kind of quirk he could truly become the greatest hero of all.
Plus when you consider One For All's greatest weakness, a revive quirk could fix that. Assuming Deku's quirk is added to the mix he could still go on passing his quirk to others to continue the line of successors. They wouldn't have to worry about dying young because of the revive quirk. Or depending how the author decides to write it, he could presumably live forever.
I know this is all kind of wishful thinking but for awhile now I've thought it would be cool to discover that Deku actually had a quirk all this time, and the only reason we don't know about it yet is because it only activates upon his death because its a revive quirk.