Shimai Don ~Shirudaku de~

A high school sweetheart couple tied the knot, living a blissful and adventurous sex life. The wife works as a restaurant manager, supporting the family while her husband handles the household chores. The wife is always up for fun and never turns down her husband's advances. But their peaceful days end when the wife's college-student sister moves in. As curiosity grows, a secret relationship begins to bloom between the husband and his sister-in-law, leading to an amazing voyage.