It's Halloween in the Infinity Castle! It was Douma's idea (Muzan still blames Akaza).

Muzan: Dressed as a vampire Akaza this is your fault

Akaza: Dressed as a werewolf? WHAT?!?!

Douma: Dressed as a priest Now now, Akaza-dono, don't get mad at Lord Muzan~

Hantengu: Dressed as a plague doctor, and being afraid as usual

Daki: Dressed as a witch

Gyutaro: Dressed as Frankenstein's monster

Gyokko: He might as well just be himself.

Kokushibo: No one knows what he's dressed as, but it's very fancy ouji fashion looking

Nakime: Not dressed up.