After closing time, Mizuki, a married cleaning lady, begins masturbating while on the job. Lost in the pleasurable sensations, she fails to notice an employee returning to retrieve a forgotten item who catches her in the act. Panicking, she tries to hide what she was doing, but immediately notices the man's obvious bulge and her self-control shatters instantly. In the empty office building, the cleaning woman's moans echo through the silent rooms.