Yuriko remarries a man who has a young son, becoming a stepmother. As newlyweds, her husband is energetic and virile, while her stepson is rebellious toward his father. This family dynamic takes a dark turn when Yuriko is locked in a cage and subjected to a life of training as a sexual pet. The once gentle yet dominant stepmother is now completely dominated and kept like an animal, forced into a life of submission. Her helpless surrender gives rise to a twisted new family hierarchy.