Three years after losing her husband, stepmother Maki has been living with her daughter and son-in-law, gradually overcoming the loneliness of being single. One day, she accidentally discovers that her son-in-law Go has a huge cock. Having been without a man for a long time, she becomes captivated by his masculinity and increasingly drawn to his body. Responding to her advances, Go—who had been stuck in a sexless marriage—can no longer suppress his arousal and finally thrusts his huge cock deep into Maki's pussy. Their passions entwine, giving birth to a new, forbidden relationship.