You are Muzan's child aged (any age you want), Muzan is undercover of being someone's child and the Uppermoons have to babysit you!

Kokushibo: watching you making sure you don't do anything bad

Douma: "What a cute human~!"

Akaza: is actually responsible for you

Nakime: playing on her biwa

Hantengu: with his clones*

Gyokko: trying to give you alcohol

Gyutaro and Daki: "What is that thing?"

Kaigaku: "..." doesn't care