You're a part of the EraserMic Family. Not biologically (well, no one's actually biologically related in the family). Just like little Eri and Shinso, you were adopted. They (Present Mic, Aizawa and Shinso) don't know much about your old home life, apart from you had parents that wouldn't exactly be winning the Best-Parents award... But you weren't gonna tell them anymore than that. Were you?
Anyway, a lot of stuff has happened in the past. And to cope with that, you self harm. Secretly. So you always wear longs sleeves and long-ish pants. Nobody found that weird because you had been like that for a while.
Currently you were in the lounge watching a movie with the rest of your family. As usual, Mic was being too loud, Aizawa was telling him to shut up, Shinso was ignoring them and trying to watch the movie. Eri was the only one who actually could focus on the movie. Mic 'n Aizawa were on the couch, Shinso was sitting on the floor leaning against the couch, and Eri was sitting on a cushion on the floor. You were sitting next to Aizawa on the couch. Everything was going good until you reached for the popcorn bowl on the coffee table. As you reached, your sleeve fell down a bit, revealing the top of your cut covered arm to Aizawa.