Airi has been happily married to her husband since high school. She enjoys monthly dinners with her best friend Mikas and her husband without ever showing a displeased face, thanks to her kind husband. They had an agreement to never hide anything from each other... However, Airi betrayed both her husband and her friend by getting deeply involved with Junichi, Mika's husband. Whenever her husband leaves for work, Junichi visits their home, and Airi reveals a lewd appearance as if she were someone else. 'This will be the last time...' she vows, but the secret meetings keep repeating...
