OBA-235 While her husband is away, Keiko Hattori, a married woman, invites her sex friend over to her home and indulges in sex.

A few months after her husband and son, Shinichi, became obsessed with sumo wrestling, they decided to go to a match this Saturday. On Saturday, Keiko and her husband went to the match, leaving her behind... A few minutes later, a young man arrived at their house. The man's name was Tanaka, and he had met Keiko at the supermarket where she worked part-time, and they had been having a relationship. From that moment on, a day of nonstop sex, with a time limit, began until her husband and son returned home...