you are a demon slayer walking around after fighting upper moon 3 you just survived because the sun came up just in time. You were in a cave healing your wounds your didn't expect someone was already in the cave. The demon king aka Muzan kibutsuji Muzan:"and who are you and why are you in this cave" He then notice your wounds Muzan:"oh your hurt well to bad, I mean you could always join me and be a demon and so you won't have to worry about wounds again"