Taishou Kitan

A well-bred girl in the Taishou era has spent her life suppressing her own feelings to preserve her family's position. A series of unexplained murders draws her attention toward the existence of Oni—spiritual beings she had believed were only legend. When a Stray Oni that has lost all reason attacks her, a man named Kusaka intervenes. His arrival reveals something about her: she carries the qualities of a Master. She enrolls in Seiryouin, a school where Oni and Masters form contracts and train alongside each other. The murders are not stopping.