Hoshina is a musician who dreams of success with his band but finds himself unable to write love songs. He spends his days working at a convenience store, feeling stagnant and disconnected from the emotion he needs to channel into his music. His perspective shifts when he becomes drawn to Seto, a younger coworker whose sincerity and warmth stand in stark contrast to Hoshina's jaded worldview.

One rainy night, Hoshina discovers a sad and drenched Seto outside the store and offers him shelter. What begins as an act of kindness leads to an unexpected physical encounter between them. The following morning, Hoshina is shaken to learn that Seto is not a college student as he had assumed, but a senior in high school. Overwhelmed with guilt and regret, Hoshina immediately tries to end things, believing that any relationship between them would be inappropriate due to their age difference and differing levels of maturity.

Despite Hoshina's efforts to distance himself, Seto refuses to give up on his feelings. He continues to pursue the older man, convinced that his affection is genuine even as he struggles to be seen as an adult. Hoshina, in his awkward and earnest way, attempts to hold firm to his boundaries, believing he must protect Seto from a potential power imbalance. The emotional push and pull between them becomes the central conflict, as both find they cannot stop thinking about one another.

During their time apart, Hoshina is finally inspired to write the love song that had always eluded him, channeling his conflicted feelings for Seto into music. He performs the song at a concert, which Seto attends. The performance serves as an emotional turning point. After Seto graduates from high school and some time passes, they are eventually able to reconcile and begin a genuine relationship on more equal footing.

The story is set in contemporary Japan, moving between Hoshina's small apartment, the convenience store where both characters work, and various music venues. The narrative arc follows Hoshina's journey from creative block to artistic breakthrough, driven by an unexpected connection. Seto's arc focuses on the painful experience of having his feelings dismissed due to his age and his determination to prove the depth of his love. The theme of music runs throughout, functioning as both a metaphor for emotional expression and the literal medium through which the characters finally bridge the gap between them.