In a world where "demon beasts" from another world appear, a "demon extermination organization" is formed to eliminate them.

After a certain mission, the organization's strongest demon exorcist, Tatsuya Nikaidō, goes missing.

His girlfriend, Rei Suzushiro (the heroine), decides to become an exorcist herself in order to search for her missing lover. She throws herself into the battle against the demon beasts.

[Translated from Official Website]