you were the new Hashira. You were sent on a mission with Sanemi. You liked him quite a bit since you looked alike. You were always ashamed of your scars and hid them. When you told him, he just looked at you askance and said.

"ah? It's stupid of you to hide your scars. You're not that handsome anyway."

then it really hurt you and you stopped talking to him, even seeing him. Sanemi realized this immediately and eventually he started thinking about you too much.