High school student Yosuke, Hidetoshi Nishijima, spends most of his free time by a floodgate, coaxing the same short tune from his acoustic guitar. He is often joined by a classmate, Yu, Hiromi Nagasaku, who hums along to the melody and helps carry the mood of his music. Yu shares the tune with her elder sister, Sayuri Oyamada, who is mourning the death of her boyfriend, and through Yu, a delicate connection forms between Yosuke and the two sisters. As the days unfold, Yu arranges a few meetings between Yosuke and her elder sister, hoping the music might bridge the gap created by tragedy. During one after‑school moment, Yu kisses Yosuke, but he steps back, leaving Yu with a sense of loss and confusion.
As their story takes a darker turn, Yu’s elder sister is walking toward Yosuke when a truck suddenly strikes her, and she slips into a coma. The shock of the accident shadows Yu, and she tells Yosuke that she longs to hear his completed song when it is finished, tying the two of them to a musical promise that time cannot erase. The incident reverberates through Yu’s life and reshapes the meaning of the tune they shared.
Seventeen years pass. In Tokyo, Yosuke has become a music producer who works behind the scenes, shaping sounds and guiding other artists. One night, he intervenes when a man interferes with an intoxicated woman lying in the street, taking her to recover in his apartment. The moment is quiet and humane, yet it signals a shift from the schoolyard guitar to a more adult, complex world of responsibility and risk. During a break at the studio, a woman begins to play a few notes from the song Yosuke played in his school days, and he realizes, with a stirring recognition, that the performer is Yu.
They return to Yosuke’s apartment, drink sake, and the conversation deepens. Yu confesses that her elder sister remains in a coma, a truth that keeps a distance between memory and present reality. The moment is intimate, tender, and painful, and they share a quiet, fragile kiss as they acknowledge the pull that history still holds over them. Afterward, they visit Yu’s elder sister in the hospital, where Yu eventually takes leave at the train station, leaving Yosuke with the promise of the finished song and the possibility of a final, healing performance.
To reach that moment, Yosuke searches for Yu in the memories they built together, and he calls her number from a phone book, expressing his desire to play the completed composition for her sister—an act that binds past and present through music. On the way to meet Yu, Yosuke is stabbed by the criminal, Ryo Kase, the man he had previously shooed away from the intoxicated woman. He collapses in the street, bleeding, while Yu waits, immobilized by a mix of fear and hope. The film builds toward a quiet, aching pause as Yu visits Yosuke in the hospital and repeats that she loves him, with Yosuke replying that he loves her as well, confirming that the song’s memory has finally found a form in their shared sincerity.
