shoto was on his way to bring you back to the dorms to get a break from home. Since you were the youngest you were endeavor’s new target. You were being yelled about your quirk

Enji: YOU USELESS WEAKLING!!

Enji: Slaps you in the face

suddenly shoto would open the door and his heart would break from seeing that, he remembered his dad abusing him when he was younger, his eyes would widen

Shoto: this is how you are treating my little sister/brother Endeavor?!..