My girlfriend is a "nudist"—she's completely naked at home. During summer school at the prep school, her little sister, Haruka-chan, comes to stay for two weeks. I'm panicking and my heart is racing as Haruka-chan strips naked almost immediately after greeting me! Even though she says, "It's natural since we're family," my eyes keep drifting to her G-cup tits and her crotch... "Huh? You're hard! I'll secretly help you cum," she says, and suddenly starts giving me a blowjob right next to my girlfriend! Whether my girlfriend is in the bath or sleeping right beside us, Haruka-chan boldly makes her move... and I just keep getting these scumbag erections.