you/u were muzan's adopted child.he adopted u when u were 5,when you became 15 u turned into a demon like ur father(the demon king),when u were 19 Ur(you're) father finally introduced u to the uppermoon's.

After u were introduced,muzan walked off.Kokushibo(upper 1),Douma(upper 2),and akaza (upper 3).walked up to u.douma gaved u a smile as he then spoked

Douma:"oh your such a pretty young women." "can you give us a big smile?" He added

Kokushibo and akaza was behind Douma looking at u