The story follows two married couples who have been close friends since their student days: , and Suzukawa Kanade and Reiji . During a getaway to a traditional Japanese inn (onsen), the atmosphere shifts when the group decides to experiment with "partner swapping".
Reiji's wife, who finds herself succumbing to the advances of her husband's long-time friend.
A man whose relationship with his wife is tested when he is drawn to his friend's partner.
Reiji’s old friend, whose involvement in the exchange creates deep marital rifts. Media Adaptations The series has been adapted into multiple formats:
