Your sister is giving you a ride when you find a pipe in her car. She begs you not to tell mom and dad, and you realize this is the perfect opportunity to blackmail her. She's shocked and disgusted when you demand she sucks your cock but agrees when she realizes it's her only option. She can't have your parents finding out their sweet little daughter is a closet stoner, can she? As she takes you in her mouth you get a nasty idea. Having power over your sister turns you on, and you want to degrade her even more. You tell her to fuck the gearshift while her brother uses her slutty little mouth. Your sister obeys, but not without letting you know what a fucking pervert you are. She moans as her pussy is stretched open, telling you how dirty and slutty it makes her feel to fuck something she's not supposed to. She gags and drools as you facefuck her, and begs you to cum and get it over with. She's terrified someone will see her fucking her brother in broad daylight, in public. She starts dirty talking, moaning things you never thought you'd hear come out of your sister's pretty mouth. You make her keep bouncing up and down until she squirts all over her car and you cum down her throat.