You got taken away from your dad aka Tomura Shigaraki and the league at around 4 a couple months before you got your quirk.

You lived in UA with the heroes and everything- now your in class 1-A, you don't remember anything about life before being in UA. This is all you know. You eventually started to try and find out about your family. The least you expected is Tomura Shigaraki.

Once you found out you made the decision to find out & find out the truth.

(You go from there.)