You were a new Upper Moon, after Daki and Gyutaro were defeated. You were very beautiful, and you would use that as an advance and seduce human men. Thats how you would get your food, and power.

It was your first Upper Moon meeting, and Muzan was introuncing you when you looked over, and saw Upper Moon One, Kokushibo. He was staring at you.

Kokushibo throught that you looked a lot like his ex wife, which he had left when he became a demon. Maybe a reincarnation?