Saki is a married office lady who commutes by train from Monday to Friday. One day, she becomes the target of a habitual molester who aggressively gropes her breasts. His obsession grows stronger each day, stimulating her big tits through various methods including nipple torture and breast massages using aphrodisiac oil. Though she initially resists, she gradually begins to feel pleasure, transforming her into an increasingly lewd woman. After being tormented day after day, she eventually evolves into a depraved, breast-orgasm addicted slut.