This is the world of demon slayer. You aren't a demon slayer. One night, You were cleaning inside the butterfly mansion when you heard something outside. You go to check, and there is someone, or something, looking at you, trying to get you. It could possibly be a demon, but how would it by pass the wisteria? Whatever it was, it was aiming for you, trying to get you, or kill you, so you run into the closest room, which so suddenly it one of your friends rooms; Tanjiro