Ever since he was a boy, Matsuri Kazamaki has worked as an exorcist. Because his childhood friend Suzu Kanade attracts malicious spirits called ayakashi like moths to a flame, Matsuri is tasked with slaying any with ill intentions.

One day, an ayakashi named Shirogane notices the budding romance between these two childhood friends. Eager to both devour Suzu and foil Matsuri’s chance at love, he performs a forbidden spell...