"Then call Erin's sister"

Erin turns to you quickly, her face turning from dominance to total surprise.

You're changing the game.

Sure you implicitly agreed that with your new play thing Jennifer in the picture, you'd no longer be so insistent that Erin's sister should be a part of your sex lives.

But since Jennifer has no sister, you decide all bets are off. And since Erin has spent the last ten minutes tormenting Jennifer and making your cock harder than it's ever been, you decide that you're going to let your thick, throbbing member do the thinking.

And it's telling you that now is the time to take what you've always wanted.

Erin steps closer to you, still trying to keep up a dominant facade. "You said..." she whispers.

But stops when you grab her by her pretty, long, dark hair and give her a tug. Almost immediately she drops to her knees in front of you. So much for her dominant impulses.

The two of you have played with dom/sub roles before. Nothing permanent, but you've both enjoyed it. And once, you can still remember the words exactly, she said to you "I like it when you take control."

Why, exactly, you now wonder, did you not just take permanent control then? Why did you allow your sex life to go back to the way it had? Because it was always great, and wonderful and you figured there was no point in changing it.

But now you're changing it. Now you're taking control for good.

You give your girlfriend a slap across the face. And you can see by Erin's reaction that she feels total pure lust at the sensation of your hand hitting her cheek.

Jennifer just watches, her moist pussy glistening.

"Understand this" you say, your body heaving with excitement. Erin glares up at you through the tops of her eyes. You know this face of hers. It's total desire. "The next time I cum." you go on. "It's going to be shared by sisters. And if our new fuck pig can't provide us with that. Then I think we need yet another fuck pig." Erin's eyes are daggers. You can tell that she wants, needs, to be taken. You go on, "And I think that fuck pig should be your sister."

The room is silent. It's just you, your insatiably horny girlfriend and your insatiably horny fuck slut.

"What do you have to say about that?" You add, knowing nothing would be sexier than watching Erin agree to this, and knowing she's in no position to disagree.