Fuck Her Ass

You lean back into your sister and whisper in her ear again.
"And now, sis, I'm gonna teach you something else you'll learn to love."

You roughly push her the rest of the way over, now face down on the bed. You climb onto the back of her legs and spread her ass cheeks with your fingers. Her tight puckered hole looks back up at you, just above her abused pussy. You take one of your fingers and dip it into her pussy, scooping up a bit of her juices and then rub it around her asshole.
"Just getting you ready, Rachel."

You slowly insert your finger into her ass. She bucks and thrashes and cries out beneath you.
"Not there! Get the fuck off me you fucker!"
You start pumping your finger in and out of her ass.
"Oh, I'm gonna 'get off' alright."
You pull your finger out of her ass and grab your cock. You rub it up and down her pussy lips, getting it nice and lubed up. Then, you place the head of your dick against her tightly clenched ass and start pushing down on her with all your weight.
"Open up for me, bitch, give me that ass!"
Rachel lets out a loud scream as the head of your cock finally slips into her ass and the rest of your dick slowly follows. You keep pushing and pushing until you are laying on top of your sister, balls deep in her ass.
"FUCK, FUCK, TAKE IT OUT, TAKE IT OUT!"
Rachel tenses beneath you.
"Ok sis, I'll take it out."
You slowly back yourself out until just the head of your dick is in her ass, and then you slam all the way back into her.
"YOU FUCKING ASSHOLE!"
You laugh and then begin slowly pumping yourself in and out of her juicy ass. You pick up the pace and start really slamming down into her ass. Rachel is now mixing her sobs and pleads with moans and groans. You thrust completely into her ass and hold yourself there. Then you begin slowly bucking your hips, fucking her ass as deep as you can. You reach up, grab her hair and pull, arching her neck back and getting a good look at her face while you fuck her ass.

"How you doing sis?"
Rachel gasps between your thrusts.
"Fuck." GASP "You." GASP "UGH." GASP "FUCK!"
"Really? Well I'm having the time of my life up here."
You've been plowing her ass for a few minutes now and decide it's time to wrap things up. You piston in and out of her tight ass faster and faster. Your balls are slapping against her pussy, building your orgasm. Finally, you can't hold back much longer and ream your dick into her ass as hard as you can.