Kyousuke Ichimaru, a physics teacher at the high school where his 17-year-old wife Asami Onohara studies, conceals their marriage to comply with societal norms and a binding contract negotiated by Asami’s father. This agreement, born from paternal disapproval of their age gap and teacher-student dynamic, forbids physical intimacy until her graduation, forcing Kyousuke to meticulously balance ethical obligations with secrecy.

Though initially resolute in honoring the contract, Kyousuke struggles with escalating tension between his vows and Asami’s determined pursuit of closeness. His stoic facade falters under external pressures, particularly the persistent advances of colleague Iwasaki-sensei, who capitalizes on his secrecy to seduce him. A vulnerability emerges through his low alcohol tolerance, which Iwasaki exploits during a drunken encounter, jeopardizing his carefully maintained boundaries.

Their relationship traces back to his former role as Asami’s private tutor, where mutual attraction blossomed into a clandestine marriage. This dual identity as educator and spouse strains his interactions at school, compounded by his grandmother’s unannounced visit. Unaware of Asami’s age and status, the grandmother’s presence forces comedic yet tense improvisations to mask her true role.

Kyousuke vigilantly safeguards their secret, deflecting suspicions from neighbors like Sakura Mizunosaki—a single mother who first mistakes Asami for his relative before aiding their ruse. He navigates Asami’s social circle with cautious restraint, sidestepping public affection and quelling gossip about their proximity while upholding professional decorum.

Later narrative arcs reveal his resolve eroding as emotional bonds outweigh contractual duty. He and Asami mutually abandon the agreement, consummating their marriage prior to her graduation—a decisive departure from his earlier rigidity, underscoring a newfound prioritization of personal connection over societal dictates.