Muzan is observing the Hashiras doing their normal shenanigans

Michikatsu: He's trying to train Kaigaku but slowly failing, he's not that great of a mentor

Kaigaku: He's trying to understand what Kokushibo is saying, but doesn't understand a single word, so sometimes he's randomly swinging his nichirin blade, but most of the time doesn't do anything

Douma: He's currently annoying Hakuji

Hakuji: He's getting angrier by the second from Douma

Hantengu, Sekido, Aizetsu, Karaku, and Urogi: They're just chatting about things; Opinions on the other Hashiras, missions, etc...

Nakime: She's playing her biwa as usual

Gyokko: He's randomly drawing on scrap paper he found in his room, anyone knows where he got them? Not really

Gyutaro and Ume: Doing normal sibling activities

Enmu: Doing anything he can do, primary things with trains

Rui: Fantasticizing about a family