You know what they say, the most quiet ones are the most terrifying when they snap.Unless Akihito was fighting as a child soldier in Afghanistan and Sudan for years, I don't know why he would have the kind of presence that would immediately make a senior soil their pants and flee the classroom. But maybe he did. No wonder he's so focused on his studies and living a high performance life.
Well, besides the abusive part, (on which I am not sure tho) that is sadly a miss. His backstory is a bit... sad, I'd say. (Won't say, cuz Spoilers)So I'm guessing in the past, he backed up his buddy Akira in a fight (for whatever caused it) and just demolished the others. Because of this incident, their old soccer team was banned from playing for the rest of the season.
As for his family, either they cut ties with him after the incident because they were abusive before anyway, or they just were so horrified by the consequences of his actions that they couldn't come to terms with it.
That's just my guess.