The Demon Lord Returns || Demon slayer AU

AHHHHH THIS IS MY THIRD BOOK IN THE SERIES IM WRITING please go read the first ones description to understand more i don't want to rewrite it again.

(Y/n) must accompany Tanjiro and his new demon sister on their search for the man who ruined his life. Little do the two siblings know, (y/n) might be more familiar then they thought and how does she know Muzan? Find out how many people she meets and how many people she recognizes! Love might fall into this book as well