So we’ve all considered a quirk that can turn the kids into even smaller kids but have you considered:
Teenager!All Might
All Might just walking around Yuuei trying to be a teacher when BAM oops someone’s quirk turns him into a younger version of himself which happens to be around the same age as his students. Sixteen year old All Might, blooming with new youth, and he’s free once again of his enormous title and his PAIN. But he’s also quirkless once again.
He still has his memories and his experience so he’s still on as a teacher, but the difference is extraordinary. The teachers all carry a certain skepticism that his youth isn’t clouding his judgement and treat him like one of their students sometimes, but the students are friendlier and more comfortable around him as well and even more willing to tell him their problems so that he can help fix them (to varying degrees).
The media believe that he’s All Might’s long lost son (because no way is anyone outside of Yuuei is allowed to know what’s going on) and they hassle him constantly so some students form the Young Might Protection Squad to keep the press away.
AND THE VILLAINS. They view All Might’s younger condition as a way to get back at the All Might they believe is his father so now we have Young Might, quirkless and painfully ordinary, trying to fight off full grown villains out for his blood. He’s gotta learn to fight, not just with his fists, but with his whole body like he’s never had before. There is no extraordinary strength for him to rely on anymore, no ability to overpower with no need for skill and come out on top, and his fists will break if he even hits a wall too hard. So what’s he gonna do?
He’s gotta Git Gud. Martial arts lessons from Aizawa and Ojirou, basic first aid lessons from Recovery Girl, and basic shooting skills from Snipe. He’s becomes a jack-of-all-trades on the field, not the greatest hero but still a hero in his own quirkless right like his first stint as a hero. He’s a new inspiration to his students and his fellow teachers and he finds that even old dogs can learn new tricks if given the chance.
But what he didn’t expect was to learn so much from Izuku, who still looks at him like the sun shines out of his ass and that his awkward pats can heal the sick. He learns that if he limits himself to only what he used to be, he’ll never take this gift to become something newer and what he has the potential to be.
He has to convince Izuku not to return One for All back to him, because All Might’s age is done and Deku’s is just beginning. And maybe, just maybe, Toshinori Yagi’s heroic works are just beginning too.
