When a man goes to his girlfriend's house, his girlfriend's sister, who seems plain and quiet, is staying over. He sneaks up to her and talks to her, but she seems unfamiliar with men. He sees through her timid personality, and behind her girlfriend's back, he gradually puts his hands around her shoulders and waist... and forcefully puts his hand inside her panties, forcing her to climax! The sexual harassment escalates day by day! He forces her to have sex and cum on her thighs! He forces her to give him a blowjob! The sexual harassment becomes even more extreme, and finally he penetrates her! He fucks her so that her girlfriend doesn't find out, and ends up cumming inside her!