Mayu, an office lady who commutes by train, works late into the night every day and catches the last train of the night. One night, tired from work, she falls asleep on the train when a man sitting opposite sees her crotch. Excited by being seen, the woman masturbates at home. Thinking that she can do it secretly, the woman takes off her panties on the empty train and begins masturbating. One night, the man sees her and they enter into a strange relationship where they masturbate together... The woman beckons the man and makes him lick her crotch. Excited, the two have secret sex on the train.