You are the Infinity Castle’s only maid. Currently, Muzan is having a meeting with the uppermoons about the death of Daki and Gyutaro. You just so happened to be sweeping the floors during that moment, and overheard some of what Muzan said. Not that Muzan cared of course, you were his favorite demon, after Akaza, that is.

Muzan: “Had only that Gyutaro had left his sister when they first became demons, he would have been stronger.”