"Ow! That hurt!" Gina snaps as you inject about half of the growth hormone potion in her the fat of her back just above the hem of her denim capris. You withdraw the needle. You rub and then kiss the injection site, assuring your girlfriend that it will feel better soon. Your girlfriend was already "thicc"—her lower body maxing out her size twenty pants—but if this went the way it was supposed to, they might have to redefine the word.
"I hope you're right," she says over her shoulder, but continues to lay on her stomach. "This is so much further than we've ever gone before..."
You can already sense the liquid spell taking effect as it spreads further and further into her system. You cannot help but feel a thrill when the black lines of the spell's filigreed sigil rise into view across the small of her back and the first gurgles of growth reach your ears. Already, you can see a little bit of a muffin top forming. Then, there is a very loud gurgle and the first twitch of real growth happens in her thighs. Right before your eyes, the already tight stretch denim is pulled even tighter.
"I'm growing!" Gina squeed. No matter how many times you both do this, no matter how nervous she pretends to be about using magic in an erotic manner, she is always puppy-level excited when it begins. "I'm really growing!"
Mere seconds have passed and the sound of groaning fabric is already a noticeable counterpoint to the sounds of existing tissue being copied and cloned to create an escalating wave of growth. Her briefs rise into view as her spreading ass pulls the hem of her pants down. Her growing calves and lengthening legs cause the cuffs of her pants to slide up, towards her knees. The seams near her pockets are really being strained now.
She gets up on her hands and knees, and shakes her heart-shaped backside at you before sitting back on her heels. Moving to that position pops stitches in the outside seams of her pants and her thighs surge outward. Kneeling forces more of her burgeoning ass into view but her pants cannot seem to slide any lower. Her hips have already widened to the point that the only way the pants are coming off is if she bursts out of them. "Oh, this feels so good..." she groans, cupping her big-but-proportionately-sized boobs. "Way better than last time."
Her fingers move to where you had administered the growth hormone and then down around her butt. From the way either cheek is now more than she can cover with one hand, her measurements have likely grown by fifty percent at this point and the spell still has a few more minutes of growth ahead of it.
"I'm sure you want to watch your work in action..." She says, turning to face you. Her voice is deeper, darker, and more sultry than ever. Which is weird. Her voice has never changed before. Perhaps that was a side effect of the additions you had made? She shucks her t-shirt and then her bra, giving you an unobstructed view of how her body is changing. Because of how much her ass has already expanded, you can see it from the front. Pressed from all sides, the front of her pants have slid down to vanish between the curves of her cute tummy and thighs. Unlike previous sessions, her stomach does not seem to be shrinking either. Like, you can feel the magic working on her midsection, but the changes are all growth and no shrink. Beneath the swell of her chub, more and more muscle is forming. Her waist is spreading, just like her hips—although her hips seem to be gaining about twice a fast.
There is a snapping noise and the rivet of her pant's button drops to the bed between you. Her weight is pressing down into the matress. “Oh, yes!” she said through a moan as her swelling thighs squeezed tight against each other and their junction.The sensation of muscles growing against muscles only seems to fuel further changes. Her hips had already grown to be much wider than her shoulders, but they keep spreading. It was like the thickness of her thighs was forcing her frame to adapt. The jean capris were at their limit. It only took one more particularly intense pulse of growth and they positively exploded as her ass and thighs gained another twenty percent of their size in a couple of seconds.
“Mmm…this feels so good! I can't even describ-ah!" Just then, she got... bigger. Like, in more than weight sense. Her whole frame was another foot taller out of no where. The bed creaked under the sudden strain. There were only a few seconds left until the spell was finished, how much bigger was she going to get?
"Oh, shit... that's good—How long... How long did you say this would last? I want to get in at least three rounds before I start to shrink…”