Several years into her marriage, Hibiki has always strived to be a devoted and dutiful wife. However, her relationship with her husband continues to deteriorate, and she can no longer see a way back to how things once were. Into her life steps Aoi, the husband of a close friend who lives nearby. Sharing their inner struggles, the two grow emotionally closer—until Hibiki commits adultery for the first time in her life. But she remains unaware of the shocking consequences that this act will bring.