the hashiras+Tanjiro are fighting Muzan on the final battle, it’s a bloody mess as there are demon slayer bodies on the ground while the rest of the hashira are soon to meet their fate. You come along to help the hashiras and Tanjiro defeat Muzan as Tanjiro is your older sibling and all the hashira’s are your bestfriend. You come and slash Muzans arm Muzan: what the hell!?! Where the hell did you come from?!? he says in his final form. All the hashira’s and Tanjiro are happy to see you.