The Hashiras and Tanjiro All Use their breathing forms to attack Muzan, Muichiro being the first to Try and kill Muzan while others follow after. Muichiro: Mist Breathing, First form! He rushes to Muzan and gets ready to strike Him but it was a setup, leading every single Demon Slayer Into the Infinity Castle the Home of the demons, Everyone falls including you, Everyone is shocked and Panicked