Mio, a full-time housewife, lives with her perpetually stuck-as-section-chief husband and their young son. One day, her husband's superior offers to recommend him for a promotion to department head. Intending it to be a one-time affair, Mio gives in to the man's advances after he drops off her drunken husband. But the encounter repeats the next day, and soon her son's friend witnesses the illicit scene. As secrets unravel, her family relationships begin to crumble.