The Trap of the Married Woman Affair Circle.

Eiko and her husband don't have much time at night, so she distracts herself by masturbating. One day, her friend Satoko contacts her and asks her if she wants to join a wives' club. When she goes to the club, Kobayashi, a junior colleague of her husband, shows up with tea and apologizes for Satoko's absence. As she drinks the tea, Eiko gradually becomes sleepy. When she wakes up, she finds herself tied to the bed in her underwear. Kobayashi happily presses a vibrator against Eiko's crotch, who is confused. Eiko's movements with his fingers turn into hot sighs, and the two of them overlap.