Wait huh? Did I forget something or has it been stated how many other incidents, besides his sister almost killing him by accident and his mother's "clumsy" neglect, he has been involved in since he was a child?
like WTF that makes him being so "based" actually feel even slightly more realistic, what with being put in the worst of mix-ups that consistently, for that long a time. But I can't really remember any other.
During this timeline there is only 3 major incident happened to him, it start with Yukito's mom neglect who kept ignoring him despite Yukito's wanting her attention, to which at some points Yukito instead of blaming his mom he turns out blaming himself for being such a needy child, he start thinking that if only he never born his mom could focus on his work (he's around 7 years old btw), thus he decide to never bothering his mom anymore which resulting to his current relationship with his mom.
So Yukito turned to his sister for attention, at first his sister accept it gladly, but shit happened that Yukito's sister ended up pushed him down from above a jungle gym, then she run away leaving Yukito bleeding out (her sister is still at elementary school)
After the fall, Yukito then assume that both of his family wanted him die, so he tried to off himself immediately afterwards
The 3rd incident is happening during the week between his fall from the jungle gym until he founded at another city gotten all beaten up (this one is a spoiler for the future chapters)
That's why after they found Yukito at another city, his aunt lash out at her sister (Yukito's mom) for being a terrible parent and proceed to try in taking custody of Yukito, he only taken custody by his aunt for a few months and then back to his mom & sister afterwards.
This school incident is happening after all these 3 incident, right before that childhood friend faking about having a boyfriend.