"I want you to transform into an 8 inch long cock, placed just above my pussy. I will feel everything you do, though I will be able to control the level of sensations I get from it. You will also not cum until I tell you that you can, and not be able to get my precious Valerie pregnant. Lastly, if I grab you around your base, pinch you, and pull, you will come off, and attach to anyone, anywhere I please."
Jenny stood there in shock for a few seconds, then slowly started to notice the transformation beginning. It was just as quick as before, only this time, the sensations were much greater. When she felt her orientation and placement change, she realized she was "looking down" on her sister, only she looked far bigger once again.
Then she felt somebody touching her, and she writhed in ecstasy. This was FAR better than she had ever felt before. She could feel the sexual energy pulsing through her form.
"Mmmmm, that feels wonderful... Get over here Val, and help me take care of your sister."
Valerie was fascinated by this latest twist in her relationship. It was a little odd, but overpoweringly erotic. She was decidedly lesbian, but there was just something about a cock that got her just a little more wet down below. The idea of submitting to the power of such a powerful sexual organ was enticing, in a way that the female form just couldn't replicate. They had played with different toys often enough, but it was nothing to the feeling of having a real live, pulsing cock right before her. The fact that it was her girlfriends cock made it perfect.