My father remarried and my new mother, Sayuri, came to my parents' house. At the same time, I went to a university outside the prefecture and decided to live alone at the boarding house without much conversation with Sayuri. And when I returned home during the winter vacation, I decided to hold a Christmas party with my parents. The two who had drunk fell asleep with a kotatsu, and I kissed the defenseless Sayuri's lips unintentionally. At that time, I was struck by the pleasure of melting my whole body.