Hiroshi, who visited his girlfriend's house after dating for a year, met her "girlfriend's mother" for the first time, a beautiful, kind, and hardworking woman who raised her daughter alone in a single-parent household. Apparently, that day happened to be her mother's birthday, so Hiroshi was invited to join her and her mother for a birthday celebration that night. And thanks to her mother's kindness, Hiroshi ended up staying at his girlfriend's house that night...