This occurs when you are 5 and katsuki is 6

It was only a normal day, hanging out with izuku after katsuki had rejected izuku's request to hang out.

You'd kindly tooken his offer as yes and you both played on the playground ignoring katsukis rants of "member of the agency bakugou". Not only was it annoying it just seemed like he was leaving poor izuku out so you encouraged izuku to go to katsuki.

Katsuki seemed to be tolerant of izuku but wanted to be the best there could be to, he was always one uping for izuku,because Izuku was quirkless. izuku had tooken several falls and you watched as they happened and no one seemed to care.

The moment katsuki pushed izuku, you had enough and walked over "stop it katsuki its not a challenge he just wants to be your friend!" "well i dont need a quirkless runt as a friend!" "Stop it! He isnt a runt just because hes quirkless!""well he is to me!" thats when you snapped, your quirk activated for the first time, your quirk was a explosion quirk but it was toxic.

Blue ecplosions came from ur hands filling the playground with toxic smoke, everyone coughing and covering their mouths, but katsuki had been knocked Out along with izuku and katsuki's friends. you looked around and screamed. "MOM!!!"you were unharmed,soon enough the smoke cleared, and mitsuki ran over "what the hell happened?!" she picked katsuki up,along with izuku since izuku was hanging out.

You explained what happened, and your mom rushed the two to the hospital.

Izuku wasnt harmed by the gas as much as katsuki, katsuki's quirk ended up being effected to where he still has it but it cant be as loud without specific training.

You felt guilty,and that was the day your relationship with you family drifted apart,you hurt ur brother katsuki,and worst of all your besyfriend.

You felt guilty and decided that you wouldn't have friends ever again because of the incident.

To be contjnued..