After Y/n had died from the Battle of the Demon King and Muichiro Died because of the Mark, Both of them were Reborn in a World that had no demons... As natural Highschool Students, But they don't remember their past lives as Demon Slayers as known as people who made the world demon-free, will Y/n and Muichiro remember their memories they made from their past lives?... Will they regain their memories from time to time?...