You're getting what you want, kinda

After a few minutes you feel sweaty. You keep scratching different parts of your skin. Your tongue is dry. Your balls ache with pain. Your cock is strained.

"Look sis is there anything else you need? Or can I go?" You say urgently trying to find a way out of here. You need relief. And what relief brings you. You need, your cum.

"Okay, so" She puts the manual down and grabs her phone/your cock. "You are what, 3ish drinks into yourself? Well, I hold the cards here. So take off the ring. And give it to me." She smiles. Holding her phone close to her face, licking your base. You moan. in disbelief you are being tempted but also, want to know why.

"Why? what are you going to do. Why do you want to take it from me?" You ask jittering and struggling.

"You obviously didn't read the manual. At least beyond what was relevant to your gender. You won't lose the feeling that you crave right now. But I need you to give me the ring. Do you want me to swear?" She says all this tingling your dick ever so lightly. Your sister hasn't done you wrong before. Reaching down you remove the ring. Slowly you feel the pain of 3 orgasms over the course of a few minutes. Your balls fall out from under the ring. Aching. Your dick collapses, strained to no end. Once it's off it slides right off her phone. You toss the ring to her. She grabs it and tosses it back at you.

"I don't need both. God you suck at reading the manual." She says. Bringing the ring to her mouth she whispers something to the ring and gives it a squeeze. You feel it vibrate in your hand. You see her lower her shorts, kicking them off the bed. Completely exposing her pussy. You begin moving a hand to your dick. "Like what you see? Well you'll love this. This is what you wanted after all." You see her move the ring down to her mound. She places the ring against her mound with some sense of trying to press it in. After a second she lets go of it and moans, Slowly you see out of her mound, pushing out, flesh pushing forward. Slowly she started to gain an inch, or two. The tip begins changing color, getting bigger. Slowly it grows. Another bulge grows underneath, getting fat, not long. After a few seconds it stops. During all of this she is in screaming ecstasy. Rubbing her breasts she comes to a thunderous orgasm. And out of the flesh comes fluid. Cum. Your sister just grew a cock.

"Well, ready for the cake?" She reaches down. Grabbing the ring she pulls it out from under her balls. Off of her member. But it stays, "Now, the Icing." She slides it back down. And in your very hand. Her dick comes through the ring.