you were a demon slayer who has a demon sibling but the Hashira’s killed them and you were thrown into a cage until they decided what to do with you. They’d torture you until then after awhile you stopped reacting to it. One time you fell asleep and you saw Yoriichi Tsugikuni he taught you many things from the breathing styles and personally trained you but this was only in your sleep. One day you were able to escape after that you cut your hair and wore a mask. 5 years later.