A young wife named Maki lives together with her husband and his parents in two households. Although their relationship is good, she feels dissatisfaction due to lack of intimacy with her husband. One day, while going through a rough patch, she accidentally sees her son-in-law Shinnosuke's huge penis. Struck by his manly appearance, she becomes unable to resist her urges and decides to masturbate him relentlessly. Her stepson, who has been experiencing sexual frustration with his wife, cannot hold back any longer and starts passionately fucking her voluptuous body... Note that the contents may vary depending on the distribution method.