Three years have passed since the end of the Great War against monsters invading from another world. Reports of 'Mabito'—humans whose bodies have been partially parasitized by monsters—are surfacing worldwide. Amidst this, Hayato Senju, who was supposed to lead a promising life after getting into an elite school, has his 'Mabito' abilities manifest during a date with his fiancée! Once exposed as a 'Mabito'—a power considered abominable—Hayato is stripped of his elite status, kicked out of his home, and forced to join 'Mabito Juku,' a private school that gathers those like him. There, alongside fellow Mabito Kohei Onigashira and the school's headmaster, Ki Tsukuma, he begins a new life hunting monsters, but...!