Konatsu, who has recently become interested in sexual acts, is troubled by her large breasts despite her petite frame. One night, she finds it exhilarating when a man on the last train catches a glimpse of her cleavage, and she starts intentionally showing it off daily, relishing the attention. One day, when her cleavage is discovered, she hides on the train and gets hand-jobbed. Their relationship progresses to the point of having sex... Unable to cool down from the excitement, the two leave the train and continue having sex at a hotel until sunrise.
