So exactly what’s going to happen when Hachiman Hikigaya, an isolated high school student with no friends, no interest in making any and a belief that everyone else’s supposedly great high school experiences are either delusions or outright lies, is coerced by a well meaning faculty member into joining the one member “Volunteer Services Club” run by Yukino Yukinoshita, who’s smart, attractive and generally considers everyone in her school to be her complete inferior?

Tanjiro Kamado, joined with Inosuke Hashibira, a boy raised by boars who wears a boar's head, and Zenitsu Agatsuma, a scared boy who reveals his true power when he sleeps, boards the Infinity Train on a new mission with the Fire Hashira, Kyojuro Rengoku, to defeat a demon who has been tormenting the people and killing the demon slayers who oppose it!

A spy, an assassin and a telepath come together to pose as a family, each for their own reasons, while hiding their true identities from each other.