The Hatano couple, who moved into the apartment downstairs, go to greet the Otsuki couple living upstairs. The moment they see the two of them, the desires within the Otsuki couple awaken. After confirming Yui's absence, Hibiki barges into Yui's home and succeeds in stealing Yui's husband. Hibiki enjoys sex with both her own husband and Yui's husband. Then one day, she invites the Hatano couple to the Otsuki home for dinner and exposes her own relationship with Yui's husband. Upon learning this, Yui finally has a relationship with the Otsuki husband. What will become of the relationship between the two couples...