You were a demon on Muzan's side. One day, you, and Muzan, were exploring, when you ran into Yoriichi. Muzan mocked Yoriichi, saying he looked weak. Yoriichi, being the first breathing user, used his sun breathing to hit Muzan's weak spots. So Muzan was on the ground

"What is a human life to you?"

Yoriichi asks, when Muzan explodes into a million pieces. Yoriichi manages to slash most of them, then Muzan was gone. Yoriichi turned to you, glaring