Snow has been carrying a torch for her first love for fifteen years when she attends his wedding. At the reception, her eyes fall on Shun, a novelist with a mournful look who delivers a speech on behalf of the groom. Both raw from the sting of unrequited affection, they tumble into bed together that night. Though neither can instantly forget the person they loved just yesterday, a new spark flicks to life between them. By chance, Snow ends up drinking with her first love and his new wife; the newlyweds' obvious happiness makes her feel unbearably out of place, and it is Shun who appears again to rescue her.

Snow works for a film distribution company, and her next assignment happens to be adapting Shun's novel for the screen. This professional connection transforms their casual arrangement into an office romance that quickens Snow's pulse. Shun, meanwhile, watches Snow chat with a male coworker and finds himself bothered by a feeling he does not yet name. Their link, born from physical need, begins to blur as they wonder what they really mean to each other.

Shun invites Snow to a fireworks festival under the pretense of research for his new book. She dresses in a yukata and wonders whether this counts as a real date, only for the two to run into her first love and his wife again. After the festival, they finally become official boyfriend and girlfriend. Snow, eager to reclaim the youth she feels she lost, suggests a date in her hometown, but the places they visit are thick with memories of her first love, and her constant references to him make Shun openly jealous. Later, Snow tries to visit Shun's apartment, but he refuses stubbornly, planting seeds of doubt: maybe he has another woman. When she tails him, what she discovers tests her trust.

Their relationship deepens through successes and strain. Snow throws herself into preparing the premiere of the film based on Shun's novel, and the two steal a brief, precious reunion at the screening. More obstacles follow, but they weather them. Shun proposes, and they begin planning their wedding. But Shun shows up for the dress rehearsal pale and exhausted; he is pouring everything into what he calls the novel of his lifetime. The story of two people nursing broken hearts, who together have accumulated thirty-five years of unreturned love, closes as they prepare to walk down the aisle, their bond no longer a mere salve but something genuine and lasting.