You're the child of Bruce Wayne, and you moved to Japan because your father opened up another Wayne Enterprise there. So he enrolled you to UA high.

At first, things were going good, but then your classmates bullied you because you're the child of Bruce Wayne, and they were jealous of you, so they would say things to make themselves feel better.

Eventually, you finally had enough, and left UA, and the hero to become a vigilante like you were in Gotham.

Since you left, they all tried looking for you, and try to make things right.

But that moment, they fucked up..