The serious female teacher Hinano Togawa serves as the faculty advisor for student discipline at the high school where she works, constantly warning students against immoral relationships. Her biggest annoyance is her fellow teacher and childhood rival, the flirtatious physical education instructor Hayato Ohgami. The two have been a well-known pair of enemies since their own high school days, when she was a member of the disciplinary committee and he was a troublemaker, and their constant bickering is often teased by their students. The conflict escalates one night when both are working late in the staff room. Hinano accuses Hayato of being lenient with students because he engaged in suspicious behavior himself as a student, mentioning that she once witnessed him kissing someone. In response, Hayato retorts that she was likely just jealous, and then forcefully kisses her. He tells her that while immoral relationships are forbidden for students, it should be fine for teachers like them. Despite her hatred for his flippant attitude, Hinano finds herself unable to resist his intense gaze and touch.

The story follows their push-and-pull relationship as they interact at school. Although Hayato frequently teases Hinano and makes suggestive advances, he reveals himself to be a caring teacher who genuinely worries about his basketball club students and connects with those who are struggling to attend school. He has likely been interested in Hinano since their school days, but neither of them is honest about their mutual feelings, leading to a frustrating dynamic of unspoken mutual attraction. Hinano also cannot hide her own feelings, at one point calling Hayato's name in her sleep.

The plot thickens when a handsome and reliable teaching intern named Takamori, who is younger than Hinano, confesses his feelings for her. This development makes the normally carefree Hayato jealous, and the two men become rivals for her affection. As the school culture festival approaches, Hayato and Hinano are forced to wear their old school uniforms, which makes them reflect on their shared past and begin to resolve their misunderstandings with each other. After finally becoming an official couple, their relationship seems to be going smoothly as they spend time together and celebrate Christmas, but Hinano soon begins to seriously question the reality of a secret workplace romance between two teachers. Their intimate encounters take place in various taboo locations around the school, including the staff room, the physical education supply shed, the infirmary, the rooftop, and a storage room.