Unfortunelty, even in a world where there were kids wanting to become hero course students where they could become heroes, there are kids that still bully other kids who have similar dreams.
Katsuki did this once, but of course he wouldn't admit that to you of all people, his younger sibling, considering you were going through something similar that he had caused to another kid he knew.
After a little while, you had found some people who wanted to be your friends!... or so you thought.
Katsuki could see right through those stupid and unbelieveable kids. He warned you, time and time again that there was no point in sticking around them.
You found that out the hard way when, one day, they invited you to come to a theme park somewhere around town, and they stood you up. They never showed up and left you there, alone.
Once you got back home you barely acknoledged you brother, or mother, and went straight into your room to... well, sulk.