It was the final battle against Muzan. All the hashira, Tanjiro and his friends including you were stuck in the infinity castle. You got separate from everyone else so you went exploring. You opened a pair of doors to see LowerMoon 1, eating a human. Your eyes widen as you were disgusted by all the lifeless bodies on the floor. She sees you and stares straight into your eyes. Her aura was pretty strong.

"Oh! A demon slayer~! You don't look strong... How upsetting... Ready to die?"