Spring arrives at a high school where a new legend is about to clash with an old one. Third-year student Haruka Shirakawa is a cheerful and laid-back delinquent who has just unwillingly claimed the title of the school's top fighter, pushed into the position by his eager friends. However, his interest in fighting wanes when he discovers that his new classical literature teacher, Mr. Narumi, is a former legend—an undefeated brawler from his own delinquent days.

While Haruka's peers urge him to challenge the teacher to surpass the myth, Haruka feels a different pull. He becomes fixated not on defeating Narumi, but on understanding him. After watching a video of Narumi fighting in his prime, Haruka sees a fire in the teacher's eyes that ignites a deep desire within himself: to grow stronger and to mature into a man like Narumi.

Mr. Narumi, now a reformed troublemaker dedicated to his role as an educator, refuses Haruka's challenge for a physical fight. However, he agrees to a different arrangement. Instead of battling him, Narumi decides to teach Haruka how to fight, becoming an unconventional mentor. These lessons quickly transcend physical combat, striking emotional depths as the student-teacher relationship blurs into something more intimate. The dynamic explores complex themes of leadership, the weight of a reputation, and the turbulence of adolescence within the framework of a Boys Love romance that includes an explicit age gap.