In the summer of my third year of university, my mother told me to take a break because I was too engrossed in my studies, so I decided to stay at my uncle's house in the countryside for a week. In the rural area, my uncle, the owner of the house, and Rinko, a gentle person, welcomed me, and I felt nostalgic for both of them. A few days later, Rinko, who should have been living innocently, had a secret meeting with a man at the front door. With Rinko managing a man with an overwhelmingly master-slave relationship. When I was stunned by her appearance, which was completely different from usual, I was invited to teach a secret that evening.