Ichika Fujiwara is a twenty-eight-year-old office worker who keeps to herself and maintains a quiet, orderly life. No one at her workplace knows about the event ten years ago that she has tried hard to forget. Her calm routine is shattered when her former boyfriend, Kazushi Amaki, arrives at the same company as a temporary transfer employee. Their sudden reunion forces Ichika to confront the painful memory of the “sin” they committed together during their student days—a secret she has never told anyone. Despite her guilt and her efforts to keep her distance, being near Kazushi reawakens a powerful physical and emotional longing that she cannot suppress. Their suppressed desire builds until both abandon their restraint, reigniting a passionate, secret relationship.

The setting is a contemporary Japanese office environment, where Ichika and Kazushi must navigate their rekindled affair while hiding it from colleagues. The story follows the tension between their professional composure and the intense private connection they share. In the second volume, a new character enters the scene: Manabu Kokonoe, another transfer employee who turns out to be a high school classmate of both Ichika and Kazushi. His appearance brings back vivid memories of the three of them working together on a school committee, and his cryptic remarks hint at hidden motives related to the incident from ten years ago. As more people from the past resurface, Ichika and Kazushi are forced to reckon with the unresolved truths of that time, even as they try to build a new future together. The narrative arc moves from a cautious reconnection, through the thrill of rediscovery, into a deeper examination of the guilt and secrets that originally drove them apart.