Rebecca slowly swirled her hips between Ty's thighs. She was enjoying the sensation of having a softening dick be squeezed at random intervals.
Ty giggled. "I didn't know I'd be able to control it so well." He flexed his pussy again causing Rebecca to jump once more. She smiled and looked into Ty's eyes.
"I've never felt so powerful," she admitted. "It was almost like I was bigger than you. I know I'm not, but just having the power of penetrating you made me feel so in-control."
Ty's eyes widened. "Do you wanna be..."
Rebecca gasped. "No! I mean... having a penis is one thing, but I don't think I could actually go all the way." Her eyes locked onto Ty's as her mind raced. Could he actually make her a boy? A full man, actually. It was insane, but the last 5 minutes was proof enough that he really could do anything. She made a tiny squeaking noise; "ok...?"
Ty laughed. "You'l love it! Come on, fuck me more!" He began to thrust his own hips back at her and Rebecca realized her penis was still pretty sensitive. Ty's motions caused her dick to harden again, re-growing inside Ty's vagina, re-filling his internal space. Ty sighed in satisfaction. Having a full pussy was a lot of fun. He was looking forward to getting the rest of the package!
He began to gasp as Rebecca gained steam and thrusted faster. "Your thrusting... oof... makes the changes... ahh... happen. Eeee! Don't stoppppp!"
Rebecca noticed that each thrust in and out of Ty resulted in a stretching feeling across her whole body. And, in front of her, Ty was shrinking! She went from 5'2" to 5'4" and then 5'8". She stretched out her legs and wiggled her toys. She felt gigantic! At the same time, Ty had slipped down form 6'2" to 5'9".
She looked down at their bodies. There were no other changes yet, but just being the same size as him was incredibly strange. Their eyes met and they gently kissed. And yet it kept going. She popped up to 5'11" and then a full 6' before... 6'3"! Even without a measuring tape, Rebecca somehow knew that she was taller than Ty used to be. She held her hands up and marveled at their size. They were clearly larger than they'd ever been in her life. She lowered then and grabbed Ty by the shoulder with one hand and the hip with the other. Her fingers almost wrapped completely around his thigh.
"You're so tiny!" she exclaimed. Ty looked down at himself and up at Rebecca and realized just how true this was. He was probably only 5 feet tall now and he realized the woman in front of him could probably force him to do whatever she wanted. The hand on his hip was gentle but he felt the strength behind it. He felt incredibly vulnerable and shuddered. A moment later Ty realized that the feeling was turning him on even more and he moaned again as Rebecca's now-even-larger-cock continued to force its way into Ty's smaller-than-ever pussy.
"You're so tight!" she cried, hardly believing the sensations she was feeling. Ty had looked vulnerable for a moment and she was aware of the physical power she held over him. She was not used to being the more powerful partner and she was shocked at just how much she liked it. She had thought she was erect before; the tiny, scared-looking Ty in front of her had caused her dick to swell to an even larger size. She gasped and moaned at the feeling.
And she still continued to thrust. Rebecca buried her face into Ty's neck and closed her eyes. She didn't want to see what was next, but she felt it anyway. Her wonderfully jiggly breast were feeling less jiggly with every thrust. Even without looking she could tell they had gone from a C to a B and were now passing A cup status. She started to wonder what Ty's breasts would look like. He was so small! Would his breasts be tiny too?
She raised her head up and was given an answer. Ty's once-hairy chest was now smooth and lumpy. Every time her crotch pushed him up his boobs flopped up one size and flopped down a slightly larger size. She watch them blossom from minor lumps to round little peaches. And yet they didn't stop. She couldn't look away as his chest passed right through C cup into DD. How could a woman as small as him command such a large bust? It must be the magic, thought Rebecca, as she watched his nipples and areola darken and grow. She couldn't tell if she was attracted to these boobs because her sexual orientation was changing or just because they were amazing and anyone would stare. She groaned again and stopped thinking about it.
Ty began to run his fingers through Rebecca's chest hair and she almost jumped off of him from the sensation. It was the weirdest part of all of this so far!
"You're beautiful," said Ty as Rebecca watched his face soften and morph into a beautiful, feminine appearance. Her own face tickled and she realized her face had changed as well. Rebecca's arm's thickened and she watched Ty's shrink as his butt expand. This raised his crotch up off the bed and she realized it was becoming easier to fuck him. Their bodies were molding themselves to fit each other even better.
"Mmmmm" signed Ty. "I'm a... I'm... I'm a girl!" He grabbed his boobs and giggled the most feminine laugh Rebecca had ever heard, making her laugh herself. It was a deep, masculine laugh and she said "oh my god!" before slapping her hand over her mouth. She sounded just like a man!
"You have a hot voice" said Ty. "Hurry up and cum in me again, Stud."
Being called a Stud tickled something in Rebecca's brain and her thrusting sped up. "Yes... yes... yes Ma'am" she managed to gasp out, before finally succumbing and unleashing an entirely new batch of jizz into the hot little pussy underneath her. Rebecca let her body collapse and found that she covered Ty entirely, squishing his tiny frame into the mattress beneath them.