Yuka, who has finished raising her children, has been working part-time for three years. During that time, she started having an affair with Takahashi, a university student who also works part-time, and enjoyed an indecent relationship. One day, they decided to go on a company trip to a hot spring. Of course, Takahashi was also one of the people on the trip. Yuka, who has a strong sexual desire, secretly invites Takahashi to have sex in the middle of the night, but she is noticed by Kobayashi, who is also working part-time with her...