Taku and Miki got married after dating since their school days. Yui, who is the same age and a "common friend" of the two, is still unmarried and a working woman who is building her career in the publishing industry. They had a friendly relationship where she would occasionally visit their house after work and drink together. Both Taku and Yui had a "comfortable friendship where they didn't have to worry about each other" and interacted with each other as usual. One day, when Miki, his wife, went out overnight, Yui came to visit...
