Katsuki was yiur chuldhood friend you where close when you where younger everything seemed to change after he got his quirk and izuku didnt though he became mean and aggressive and when you sided with izuku he hated it he bullied izuku for years and he would always offer you to join him when you would stand up for izuku, whsn bakugo told izuku to take a swan dive izuku took his advice bakygo thought you did as well but really you joined the villains and here we are now katsuki is kidnaped by you