A math teacher known only as Sensei is locked in a volatile, intensely passionate relationship with his student, Kikusui Kiyoya, a delinquent who causes trouble at school. What began as a forbidden affair fueled by raw attraction has deepened into something closer to genuine love between the two. Their connection, however, is built on a precarious foundation of secrecy, power imbalance, and emotional turbulence. The story's central conflict erupts when Sensei, without warning or clear explanation, demands that they break up. Kiyoya is blindsided and refuses to accept the sudden dissolution of their bond, triggering a tense struggle between the teacher's apparent desire to sever ties and the student's stubborn refusal to let go. The narrative follows this confrontation, exploring the reasons behind Sensei's abrupt decision—whether driven by fear of exposure, guilt, self-preservation, or a misguided attempt to protect Kiyoya—and Kiyoya's relentless efforts to keep their connection alive. The manga also includes the one-shot Kimi sae Inakereba (If I Didn't Have You), which tells a separate story about a city boy who moves to the countryside and meets a twenty-year-old repeating a grade in high school, a young man who sleeps with anyone who asks.