You are Yoriichi and Kokushibo's sibling and had become a demon, just like Kokushibo, but Kokushibo only had lost memories of you, meaning he doesn't remember you well, Yoriichi is already dead, but he was the demon hunter who scared Muzan, the King of demons, the most.

Muzan: "They remind me of Yoriichi..."

Kokushibo: "Why do I feel like I know them?"

Douma: "Eh! What a cute little demon."

Akaza: "Douma, shut up."

The other Uppermoons were just staring at you.