"I need evidence that you've been afflicted by 'arousal induced shrinking.'"

Proudly, you heard Becky proclaim, "I think I'll need to see some proof that you've been afflicted by this, uh, 'arousal induced shrinking.'" Ignoring your angry sounding outcries, Becky bent down and spread her legs slightly, stuffing your face further into her own ass crack as she put more of her weight on you. With flexibility that was impressive for both her bustiness and her tight clothing, Becky reached between her legs and went straight for your underwear. Becky giggled when she saw that your briefs were already somewhat tight, and taunted, "Uh oh, it looks like the condition has already taken effect, Tommy!" as she lightly squeezed your cock through the wrestling briefs you had on. You didn't want to admit it, but Becky's beautiful ass in your face had been turning you on gradually, despite your irritation. You groaned, which amounted to nothing more than a grunt directly into Becky's huge ass, as she began joyfully playing with your erection. Becky smirked as one of your arms attempted to push her hands away, but she quickly put a stop to that by leaning to one side, pushing your arm behind her ass cheek, and then leaning back, crushing your hand flat against her overwhelming flesh. Now that she was free to toy with you without your interference, Becky smiled and began kneading her ass cheek into your face with one hand, just as much for her own pleasure as yours, while casually rubbing at your boner with the other hand.

It didn't take long before you felt yourself becoming dizzy. Becky must have sensed it too as she cheered, with one hand still wrapped around the bulge in your wrestling briefs, "Uh oh, Tommy! I think it's about to happen!" Then, much quicker than last time, you felt yourself shrink. You dropped from two feet to what felt like barely over a foot, almost instantly, as Becky gasped. Becky, who had been resting some of her weight on top of you, slid down the wall as you shrunk, her feet sliding forward and out of the doorway, as she fell, until she heavily landed on you once again, ass first. Becky ended up in a sitting position, held off of the ground only by your body as your legs locked painfully in place, forcing you to act like a bar-stool for this bratty girl's enormous posterior. Becky was laughing hysterically as your face sunk deep between her jiggling ass cheeks, until you felt your nose and forehead cram up against her sweaty panties. You could feel the warmth of her crotch beating against your chin, but tried to ignore the sensation.

Looking down, Becky managed to spot your now much smaller body, disappearing from the shoulders up into her ass-crack beneath her skirt, as she realized her game had worked. "Hahaha, oh my god! I didn't think you'd shrink THAT much, Tommy! Wow, no wonder you want this serum so badly..." Becky once again laughed and waved the serum around, even though you couldn't see it with your entire head buried between her flexing butt cheeks. You were trembling all over as you tried to hold up Becky's weight, not wanting to be crushed to the floor again underneath a girl's ass, as she lazily observed your predicament from her rather comfortable position. "Oh look, your little shorts are too big, now!" Becky called, before reaching down to your underwear, which had slipped around your ankles as you shrunk. Becky pulled at the briefs, stupidly yanking your feet out from under you, which caused you to slip and fall. With your head still trapped between her ass cheeks, Becky dropped the final foot to the floor before slamming down, bouncing in place from impact as she laughed again at your misfortune.

Becky stopped giggling just long enough to spread her thick thighs as far as she could (which was not very far, in your cramped changing room), and reveal your poor lower body. Becky pulled your tiny but still oversized wrestling shorts from around your feet and twirled them in the air as she said, "Sorry but I think you're going to have to get changed again, shrimp!" Becky smirked again when she spotted your erection, which was still rock hard, pressing against her quivering inner thigh. Becky gave it a light flick, and laughed when that elicited a frustrated shout from beneath her ass. With one finger, Becky began slapping your cock against her warm leg, amusing herself with the way your body convulsed after every impact. As she continued to torment you, Becky explained, "Alright, tiny Tommy. I guess you really DO need this serum, so I'll give it to you... on one condition..."