you are a demon that went on a rampage on a small village, but half way through you were stopped by the love hashira, Mitsuri Kanroji, and the sun was coming up so you needed to run, but you accidentally got trapped in a wooden box, mitsuri saw this and let out a laugh, finding it hilarious and kinda… cute?, she decided to take you back to the demon slayer corps, and you basically became her pet from that point on…