Luckily she hasn't

"Oh, fuck...!" Hannah was mewling by now, while the fucking continued, and she strained against her bonds like she truly enjoyed her own helplessness. "Oh, Jeff...! Please fuck me harder!"

"You got it, babe!" Emma just grinned to herself, making sure not to say it out loud and risk blowing her own cover again, now that she knew her little sister had't noticed the swap yet. Then she happily obliged to Hannah's demands, and grabbed firmly onto the girl's hips while starting to pick up the pace.

Soon she was hammering away at her sister's little pussy like there was no tomorrow, and could just barely keep from moaning in pleasure herself at the sensations flowing from her new appendage through the rest of her body. If she'd known it could feel so good, she might have wished for a cock of her own a long time ago - if she only knew how to get one.

"Oh fuck, oh fuck...!" Her sister kept squealing, accompanied by the squeaking of the bed, and was obviously enjoying the pounding just as much as the (wo)man on top. It still seemed to surprise her however, when she was steadily brought over the edge to a most intensive climax, and it filled Emma with a sense of triumph as she knew full well how rare it was to get off without any outer stimulation of a woman's clitoris.

With the sudden increase of tightness, provided by the muscular spasms of Hannah's orgasm, it wasn't long before Emma too could feel herself reaching her peak. The sensation was beyond comparison of anything she'd ever felt before, and she couldn't tell for sure if she was screaming out loud in passion, or managed to keep it to herself while she buried herself deep and starting pumping her sister full of her sticky hot cum.

Afterwards she just sat there, bracing her hands against Hannah's back, while they were both panting and gasping to regain their breath. The sensation of her cock still throbbing inside of her sister's pussy was priceless, and again she could just barely keep from giving her identity away, this time by laughing at the absurdness of the entire situation - and even more so as she realized her new 'little friend' seemed to refuse to deflate just yet...