The Imperial City Onmyou School—a three-year, fully residential educational institution that trains officers for the state exorcism agency, the "Imperial Onmyou Bureau." Yakou, Issei, and Reiji are second-year students at this school. One day, after injuring the son of a military official, Reiji is pushed to the brink of expulsion. Yakou and Issei negotiate with the principal to save Reiji, but as a condition for canceling the expulsion, they are ordered to investigate and capture "Semimaru," a mysterious masked man who has been attacking the upper class...