Two middle-aged people, Tatsuya Urayama and Naoko Hayase, reconnect at a class reunion held thirty years after they left Hiroseyama Junior High School. He is married and works at a factory, while she has divorced and returned with her teenage daughter Kaori. Naoko now runs a bar called Coquille, a name she chose from a line in a Jean Cocteau poem: “My ears are shells, longing for the sound of the sea.” The line had been inscribed inside a poetry book that young Tatsuya gave her as a graduation present (along with a white shell). Naoko treasures both gifts, and while she once harbored a crush on him, the two never became a couple.
At the reunion, Naoko recognizes him instantly, but Tatsuya initially struggles to place her. A few days later, he visits Coquille with his friend and boss, Satoshi Kuroda, who has recently been demoted. As they talk, Tatsuya and Naoko grow closer, and the visits to the bar become a regular if quiet ritual. Yet troubles loom: Satoshi, pressured by his demotion and a looming transfer to Tokyo, attempts suicide. He survives and is hospitalized, and Tatsuya watches his friend’s life unravel as his family dynamics crumble in the aftermath.
During this tumult, Tatsuya runs into an old classmate, Jiro Tanikawa. He learns that Jiro once had a physical relationship with Naoko, prompting Tatsuya to retreat from the Coquille bar and even consider moving to Tokyo with his wife. Unbeknownst to him, Naoko continues to wait and hope. She eventually makes pomegranate wine and visits the factory where Tatsuya works. There, she confesses a memory: on the eve of their junior high graduation, she whispered a confession to him at Kurakakebashi Bridge, but he could not hear it because of a childhood illness that affected his right ear. Naoko reveals that she has thought of him ever since that moment, even through the years of marriage.
Realizing he is still drawn to Naoko, Tatsuya takes a break from work, pretending to be on a business trip, and goes hiking with her. They reminisce about their youth—recounting both the mountain they climbed as teenagers and memories of a school marathon. The two become lost on their hike and miss the last bus back to town, choosing instead to stay at an inn. After dinner, they go to bed together and awaken to a shared bath in an onsen. Naoko’s dream seems to have come true, but guilt haunts Tatsuya for stepping outside his marriage. On the road back to town, he plans to confess all to his wife, but Naoko stops him, insisting that she does not want to ruin his happiness and that she will end the affair even though she has found true love with him.
Tatsuya ultimately moves to Tokyo with his wife, trying to rebuild a life that accounts for what happened. Later, in winter, he learns from Jiro that Naoko was killed in a traffic accident when a truck skidded on ice. He returns to his hometown to visit Naoko’s grave and meets Kaori there. Kaori reveals that, as Naoko drew her last breath, she whispered “Urayama-kun,” her nickname for Tatsuya. At the next class reunion, a moment of silence is observed for Naoko, and in the quiet corner of the room, Tatsuya is found crying alone, a poignant testament to a love that both changed and haunted him.
