In the bustling Bayron City, an isolated island thriving on exploiting local resources, the emergence of 'D disasters' caused by demonic forces plagues the populace due to orgonium mining. Leading a struggling private military company is Shuu, whose reckless spending habits keep him perennially broke. Kisara, a demon girl, supports Shuu through odd jobs at his office, her concern for him unwavering. At a local high school, Kisara juggles tasks seamlessly, from administrative duties to household chores. Meanwhile, Ayano, Shuu's ex-girlfriend and a skilled operative from a prominent PMC where they once worked together, adds a complex layer to their intertwined past.