Rei Suzuki never liked working at the family shrine, but it was mostly a peaceful life until one day that all changed when a demon killed her parents, brother, and sister. However, not all is lost when Rei discovers that she's able to fight back against creatures that hurt those she holds dear. Then, she gets a proposition from one Giyuu Tomioka, who arrived too late to stop what had occurred. She accepts his offer of becoming a Demon Slayer, so maybe she can keep people from going through the same experience she has.