She's embarrassed and ashamed

"Oh my god, Mia! What are you doing here!?" Tracy doesn't get up from her current position either because she's too exhausted or too shocked to do so.

"I was um... hanging out at the bar when umm.. I saw your boyfriend here and he brought me to see you." Mia is struggling to get the words out in her stunned state. She also conveniently left out the part where the two of you fucked in an alleyway, but you could tell Tracy all about that later.

Tracy turns to you with a horrified expression on her face, clearly not having planned on her sister seeing her like this.

"I think I'm going to head out now." Mia says, motioning towards the door.

You take a couple steps after her and grab her by the arm. The two of you are now just out of view from Tracy.

"You sure you don't wanna come and stay the night?" You say with a sly grin on your face.

"Not tonight thanks, I think I need to clear my head after all this first."

"Suit yourself."

With that Mia leaves the bathroom, allowing you to turn your attention back to Tracy. You return back to the frame of the toilet stall and look down on your well used slut.

"Sir, I can't believe you brought my sister here."

"She asked about you so I brought her here. Don't worry, she isn't judging you as hard as you think. Ironically, she was kind of here for the same reason as you, to pick up guys. Although you seem to have done a much better job, in terms of numbers anyway."

Tracy smiles at this comment, showing off a little bit of how competetive she's always been with her twin sister.

"Anyway, I think it's time we get going don't you agree."

Tracy nods, "Wouldn't you like to use me too before we leave sir?"

You laugh before answering, "are you serious slut, look at the state of you. You have cum all over you, as well as whatever that other liquid is."

Tracy looks down, clearly ashamed of herself. "Some guys poured their drinks on me whilst they called me a worthless whore and spanked my ass."

"Good on them. You know what, seeing as you are a worthless whore and this is all you're good for, maybe I will use your holes before we leave."

Tracy smiles at the thought of you using her and turns back around, wiggling her ass in the air as an attempt to try and seduce you. You pull your cock out of your pants and stick it straight into her ass, skipping past the foreplay and pounding her back door doggystyle whilst she's kneeling over the toilet seat. Tracy starts crying out like a whore as you ram into her ass, going at a quick pace since you had just cum whilst fucking her sister. You're barely 30 seconds into caving in her rear end when she starts begging you to cum.

"Please sir, can I cum now. I've been holding on all night waiting for you, hoping you'd come and give me permission."

"Alright slut, cum for me. Cum as I fuck you in your tight little ass." This statement wasn't even a lie made up for dirty talk. You were impressed by how tight her holes had remained over the past couple weeks despite the endless fuckings and even intense stretching during her workouts. No matter how much dick she took in them, her holes just seemed to spring back into shape and regain their original tight grip on your cock.

"Oh fuuuuuuuck! I live to serve! I live to serve!"

Tracy's pussy starts gushing all over the bathroom floor as you continue pistoning in and out of her ass, not wasting any time to slow down as she experiences an intense orgasm.

After a while of going to town on her ass you're ready to cum and shoot your load all over her ass cheeks, adding to the existing collection of jizz. As you pull out and Tracy feels you spray your spunk all over her rear, she lets out a satisfied sigh, happy to have finally pleasured the one cock she truly cares about above all the rest.

You take a moment to lean up against the wall and recover after your second orgasm of the night and put your cock back into your pants. Tracy lies against the toilet lid in a state of post-orgasmic bliss. You grab the key to the handcuffs out of your pocket (which also contains Mia's panties that you ripped off of her) and unlock Tracy, freeing her from the position she's been in for the past few hours.

"Alright slut, time to clean yourself up so we can get going."

"Yes sir, thank you sir. Thank you for providing me with this amazing experience. I couldn't have been happier getting fucked by all those men."

"I'm glad to hear it."