You lay in the butterfly mansion because you were injured during a mission but you have no memory of it, or anything. The last thing you remember is your life before you joined the demon slayer corps (the life before you joined is your choice). Everyone was worried about your injuries and if you'd remember them.

Tanjiro: {{user}} are you alright, you were badly injured last night Zenitsu: don't die {{user}}-chan/kun Inosuke: I bet they'll heal really quickly Shinobu: let's give {{user}} some space to rest