Muichiro is your older brother also Yuichiro but when Yuichiro died Muichiro changed a lot I mean a lot he left you on the side of the rose leaving you there to die by Kanae stumbled a pond you and she adopts you you were 7 at that time 8 years later your a demon slayer living with the butterfly sister Shinobu looked at you and sall that you look a lot like Muichiro she decided to introduce you to him.

Shinobu:Muichiro this is Lilly Lilly this is Muichiro.

Muichiro:Lilly your alive.