Summer break has ended and the new term begins with the school sports festival approaching. Shingo Nagata, a cheerful and openly affectionate first-year student, is now officially dating Ao Totoki, a cool and popular second-year known for his aloof demeanor and the prominent scar on his forehead. Their relationship is still new and tender, with Shingo constantly delighted by the softer side Ao shows only to him.

Shingo brings Ao a souvenir keychain, a cream bread charm, from a family trip and steals a kiss, but the lightness of the moment soon gives way to strain. Shingo is selected for the time-consuming paired dance event at the festival, reducing the time he can spend with Ao. More critically, a confident and handsome third-year named Takeo Sudou, nursing a grudge from a relay race loss the previous year, singles out Ao as his rival. Takeo begins aggressively challenging Ao to a series of athletic contests.

When a thunderstorm hits, Ao, who has a deep fear of thunder rooted in a childhood accident, rushes back to school to retrieve the lost keychain Shingo gave him. Takeo finds him and witnesses his terror as Ao instinctively grabs hold of him during a loud thunderclap. Takeo now knows Ao’s secret weakness. Rather than use it maliciously, he uses the situation to draw Ao into repeated daytime competitions, making it look to outsiders as if the two are spending a great deal of time together.

Observing from a distance, Shingo grows increasingly insecure. He overhears Takeo and Ao discussing the thunder incident, a topic Shingo thought was private between them. Believing he is being pushed away and that Ao’s special vulnerability is now shared with someone else, Shingo begins to withdraw, burying himself in dance practice rather than confronting his jealousy. Ao, in turn, is confused and hurt by Shingo’s sudden distance.

The misunderstanding deepens until it reaches a breaking point. Shingo finally confesses his fear of losing his place in Ao’s life, and Ao, frustrated that his feelings were not obvious, bluntly admits he was only irritated because another girl had been getting close to Shingo during practice. The raw confession clears the air. Their bond is reaffirmed, stronger for having been tested. The sports festival proceeds, and the couple reconciles with renewed closeness, having navigated their first real conflict and learned to trust each other more deeply.