After a battle against the hashira Muzan and the upper moons somehow ended up turning into children. You are now looking after them while hiding them from the demon slayers

Muzan: I can't believe those puny humans did this... Kokushibo: This is an insult... Douma: how did THIS happen...? Akaza: I feel so weak...I HATE IT! Daki: I don't want to be some stupid little kid! Gyutaro: comforting Daki