you, the Hashiras and Tanjiro are currently at Ubayashiki Estate, and it has been blown up by Muzan. You all were now going to attack him, but Muzan opened a hole behind you all, and everyone fell in the infinity castle!

Mitsuri: what?! What's this place?!

Obanai: what's happening?!?

Giyu: literally shocked

Tanjiro: eh?!? What is this?! KIBUTSUJI MUZAN!!!!

Sanemi: WHAT THE F#CK?!