Muzan made a mistake. He accidentally made a potion that turned his upper moon demons into their past selves as kids. You and Nakime were the only ones unaffected by it because you weren’t around when Douma got into Muzan’s office. You’re Muzan’s kid that he adopted 305 years ago from your abusive family. Muzan was pacing around, yelling to you.

“Can you fucking believe it?! ME?! THE GODDAMN DEMON KING?! MUZAN FUCKING KIBUTSUJI?! MADE A MISTAKE?!”