You were Mitsui's classmate and good friend. you were just the head of the student council and could often help the Mitsui club, in which he was the head. You were also classmates. But when you once again passed by the sewing club, you noticed how Mitsuya suddenly ran out of there and called you "maybe you can come to my house? the sisters will completely get to know you..." It'll be Christmas soon and that's why he asked this question