Board Thread:Questions and Answers/@comment-26064296-20170918060518/@comment-33871937-20171206065716

I feel as though One For All is pretty straightforward in how it works, but I admit there are some real mysteries I'd like to know the answers to.

The original Stockpiling quirk most likely just allowed the wielder to bulk up incredibly fast, or removed the natural limits to their growth. If "10 units" is the maximum muscle strength a human can have, then no matter how hard or how long a human trained they could never go above that number normally. With the original Stockpiling quirk, the 'athlete's plateau' would be removed, and the wielder could go up to 20 units, 30 units, or even 1000 units if they lived long enough to reach that point. There's probably some element of 'muscle loss prevention' involved in the Stockpiling quirk as well, meaning that if the user reached 23 units and stopped training for several years, they wouldn't have to 'get back in shape' since they'd still be at 23 units.

Given that it fused with the Successor quirk and mutated to become One for All, the next logical step in its evolution would be to change nothing about the Stockpiling quirk's functions, but automatically set the new wielder's stats to the same level as the previous wielder's. It's like New Game+, where you start the game over, but keep all of your previous character's levels, abilities, and gear.

The only real question I have about this theory, has already been asked. If it's like New Game+, then why haven't any of the previous wielders' quirks been passed on, or at least mutated One for All further? I refuse to believe every single bearer of OFA had to be quirkless - that would be too coincidental, and makes no sense considering that All Might was seriously considering making his successor somebody with one. Maybe it overrides the user's previous quirk? Perhaps the only reason the Stockpiling quirk and the Successor quirk mutated together at all, had something to do with All for One's method of forcing it on his brother with his own unique quirk. Actually, if that last one is the case then it handily explains just about everything - there likely were quirked users, but their own quirks simply didn't react with OFA since they didn't have the unique, forced circumstances that AFO created.

Redlock brings up a very interesting point by talking about the Successor quirk. I really like your explanation of how it might have originally worked - it seems reasonable and completely within the realm of possibility. This explains the 'ghostly visions' aspect of OFA perfectly. I also think it is an extremely likely outcome that if All Might truly kicked the bucket somehow, Horikoshi would use it as a way for him to keep All Might relevant to the story. Boom, Izuku has All Might as a ghost mentor. I'm almost expecting for AFO's brother to become relevant to the story again much later on, and will explain the origin of OFA in full at a pivotal moment where Izuku needs to know more, and become more powerful to face Shigaraki or AFO or something.

Who knows? Maybe AFO's brother wasn't actually all that heroic after all - maybe he's just been reduced to a parasitic lifeform who survives by siphoning the lives of his hosts, and eagerly awaits his return to the world? MAYBE THE FIRST WIELDER WAS THE TRUE VILLAIN OF BNHA ALL ALONG. Nah, that's just crazy talk... But then again, it would be climactic to see Izuku suddenly reduced to being quirkless once more at the end of the manga, after the First Wielder regained his body. Facing down the uber-powered First Wielder with only the embers of OFA left to help him stop a master plan that spanned nine generations... I for one, would be satisfied with that ending.

The main thing I want to know though, is if the Successor quirk was so unremarkable, and practically invisible to the point that even the First Wielder's own BROTHER, All for One, didn't know about it... How the hell did the First Wielder figure out how to pass on his DNA and his quirk? How would you even learn you HAD that quirk? This is just lending more credit to my insane 'First Wielder was actually an evil parasite guy' theory...