You get your first injection

You follow Bertha inside, watching her wide hips and large butt sway. Her massive balls are tucked between her legs under her butt, and they bounce off each other with every step.

“Sam, I can feel your eyes glued to my ass,” Bertha giggles.

“There’s not much elsewhere to look, it’s so big!” You laugh.

“I can barely fit through the doorways here. Watch.” She opens the door to inside and needs to squeeze through. When you follow, despite how wide you are, you still have several inches to spare. “Told you.”

“I’m amazed. You still fit in jeans when you’re that big! Gretchen said there were some real pros on staff here for making custom clothing…”

“Yeah! They won’t put their branding on the stuff they make for us, but don’t let anyone tell you that you’re wearing knock-offs! We help their models fill out in all the right places. That’s the primary driver behind our trials. Well that and the porn industry.”

Bertha leads you into her lab and prepares your injections. You turn and feel a pinch in each cheek. Then hands on those cheeks. Then a zipper being pulled down. Then a leaking cock between those cheeks.

“Ohhh…” you exhale. “I’m so big already!” You push back and she begins penetrating you.

“I noticed! You like being filled; it’s your primary need. I accept the consequences for what I’m about to do to you, don’t worry. We have everything we need here to take care of you.” With that, Bertha pushed her shaft all the way in easily. “Forgot Gretchen fucked you all day and you haven’t had a chance to recover yet. You’re still so loose!”

“I don’t mind. I’m barely using any strength on you; it’s pure elastics at this point!”

“I figured you had a trick up your ass. Anyone else would be gaping!”

You both sigh as Bertha dumps the first massive load in your belly…

*****

After you pass midnight, Bertha seems to have expended the contents of her balls. You’re just eyeballing it, but your size seems there. Bertha pulls out and gives you a smack on the butt.

“I wonder how this will turn out…” she ponders. “Does the first serum take effect along with the second. Does the order matter? Do they negate themselves or do they both take full effect?” She stares at you.

“Uhhh…” you look at her as if she’s expecting an answer. “Guess we’ll find out next time?”

“Right!” Bertha snaps out of it. “Let me show you to the guest room…”