At Rasetsu Academy, where Oni are trained to master their blood and survive a world that fears them, a new teacher quietly joins the faculty. Known only as Y/N, she is calm, unreadable, and vastly more dangerous than she lets on. Assigned to Mudano Naitō’s class, her presence begins to shift the balance—challenging the students not just to grow stronger, but to confront what it truly means to be Oni in a world built to destroy them.