Nanami lives with her mother at her parents' home while sharing a marriage with her husband. Lately, however, her husband has been consumed by work, growing distant and neglecting their family life. One day, her older sister, Keiko, returns home for a visit with her husband, Tohru. After dinner, Nanami finds herself alone with Tohru and begins venting her frustrations about her own marriage. Tohru, too, has grown weary of his cold, lifeless relationship. Sharing similar struggles, the two gradually grow closer, their suppressed desires beginning to surface. Their emotional bond deepens into an affair, and as their feelings intensify, they take their first steps toward a new, forbidden relationship.