After saved by Tanjiro, Yuki grabs her Nichirin, and live by the promise she made to slay the demon and find the one who turned her mother into a demon. She's no ordinary, a demon eyes cursed her face, that's the only clue to find the murderer. Her family breathing technique almost become ancient, and the form ceased.
What would happen if the Dance and the earrings weren't the only things that were given to them by the first sun breather, what would happen if the Kamado family had yoriichi's nichirin blade. But not only that but what would happen if Tanjirou had learned the way of the blade and the dance of the sun at the age of 7.