You've come this far

The stereotype gun had clearly worked its black magic on your soul just as much that had turned your sister into a sexy scientific slut. Here you were four fingers already poised inside her stretchy sex. You were already in for a penny, you might as well give Alice the pound. You take a deep breath, inhaling more of her phenomenally sexy scent before you thrust in hard feeling her hyper stretchy walls give way as you bury yourself up to your elbow in your sister's snatch.

Alice gasps and screams in a mix of pleasure and agony as you literally punch up into her womb. You were somewhere no person was supposed to be, this would normally hurt, yet Alice's orgasmic expression made it clear that she was completely pleased to have you elbow deep in her womb. Her belly and sex are bulging out, your fist cleary outline in her belly as she writhes and spasms insensate in her pleasure. There's only one thing to do.

Without a hint of hesitation you pull out just enough before punching into her womb again the violent act causing is another screaming spasm of ecstatic joy. Her eyes filled with malevolent intelligence as if every time you rammed her you were giving her some kind of sick experimental knowledge. The forbidden knowledge between you was definitely growing and Alice was already starting to feel more like someone you were going to continue with.

"That's it Marky, keep it up fist me harder, beat up my insides" she gasped between squeals of absolute ecstasy.

"You can't wait for you to finish stretching me out, then I'll give you my special medication, give you a cock so big it'll break us both, I'm going to be rich and you're going to be a stud the likes of which the world has never seen, keep stretching me out Big Brother, I can't wait for you to knock me out and then knock me up. Our babies are going to be so smart.