Seven years ago, Yuto Amakawa 's parents died in a car accident, leaving him alone without a single relative, the only item left of his family being a strange and mysterious amulet given to him by his late grandmother. Ever since then, his childhood friend Rinko Kuzaki has cooked for and taken care of him. His life takes a drastic turn on his 16th birthday when he meets Himari, a cat demon samurai girl. Himari reveals to him that some of his ancestors were part of the twelve Demon Slayer families that have been slaying demons since the feudal era. She has sworn an oath to protect Yuto from the demons that are out to kill him, but Yuto's allergy to cats makes it somewhat difficult to deal with.