OVERHAUL THEORY!!
The reason he looks so young despite his age is because his body was preserved for a time by Doctor Ujiko.
Let’s say he was 3 years old when his quirk first developed and that’s when Ujiko preserved him — and he didn’t wake for another 6 years. He’d be 9 but still have the brain and body of a 3 year old.
Let’s also say that his birth certificate never changed so he looked like a super young 13-ish year old boy when the yakuza found him. He would’ve been treated like a 13 year old when in fact he was only 7.
There would have to be some sorta explanation for it though; and since Pops seems like a dismissive sorta guy he’d come up with something like, “He’s small because he grew up without proper food,” and, “He’s behind a few grades because he didn’t have an education.”
Kai looks like and acts like a man in his early twenties, not a man a few years from thirty… I refuse to believe it. Like… he’s only three years younger than Aizawa?? Nah…
