Cathy kept moaning as she pressed herself against me. She got a grip on my penis and started pumping me hard and fast before squeezing suddenly at the base of my shaft with a vice-like grip. I was startled, but even more so when I felt myself start to cum. The sticky white goo splattered against her arm and belly as she resumed pumping me slowly.
Her pussy was dripping wet; I'd slipped one of my fingers inside as she rubbed it against me. It was slick and warm and there were folds and stuff in there. I pulled my hand back and told her to stop.
"Wha- but I haven't cum yet!" Cathy whined "Please, you've got me so horny!"
"And I wish you'll always feel like this; horny as hell but unable to cum without my help!"
I took a step back and smiled at my aunt before my jaw dropped; aunt Cathy was shrinking! She had one hand over her pussy and the other across her tits, but what really got my attention was that she was getting shorter and loosing weight. She'd looked good for a 39 year old, but now she was loosing that incipient middle-age spread. Her thighs and arms were becoming slim and almost muscular. I was happy to see she wasn't loosing any weight from her boobs though, those looked just as big as they had before. If anything her now slender frame made them look bigger! That's when I noticed she wasn't trying to cover herself, she was feeling herself up and masturbating furiously!
She'd lost close to 5 inches in height and had hair spilling halfway down her back before I realized she was getting younger; She'd lost all the lines from her face and neck and looked like she was no more than 17 or 18. She was also sobbing and clutching at herself.
My wish had turned her into a permanently horny teenager who had to do whatever I said, and I was the only one who could give her an orgasm. I looked at my ring in appreciation.
"Please!" Cathy sobbed. She'd stopped groping herself and was staring at me through tear-reddened eyes. My cum and her own fluids were running down her thighs and her tits swollen from the abuse she'd been giving them. "Just let me cum, I'll do whatever you want!" Cathy shakily brought her hands up to cup her breasts, offering them to me with a whimper.
"Cathy, Cathy, Cathy," I chided her, "you're going to do that anyway! But go ahead and cum, just this once."
"Oh! Oh, Oh god!" Cathy dropped to her knees, then flopped onto her back, he legs spread as far as they'd go. "Yes! Yes! Yes!" I watched her abdominals spasm as, true to my wish, she did what I'd told her to do.
I muttered a quick wish that her tits would stay swollen and sensitive, and that she'd never get pregnant or catch any STDs--not like she was going to hear me with all the yelling she was doing. Around us people wandered past on their way to shop; nothing odd about a naked girl orgasming on the sidewalk and a boy with his cock hanging out watching her.