Living with her husband and his younger brother, Ryouko finds herself increasingly frustrated as her husband, exhausted from work, constantly avoids sex. Her pent-up desires grow unbearable until she is tempted by a younger man next door and finally gives in to a secret affair. By chance, her brother-in-law witnesses the act and takes photos, showing them to his sister-in-law. Shocked and furious, Ryouko gasps in disbelief, trembling from the guilt of her infidelity—while her brother-in-law feels an unexpected arousal. Soon, the two begin forging a new, forbidden relationship.