"...I want more of that stuff."
Okay. That definitely wasn't what she'd been expecting to hear. Mary's head lifted up, her tailfin curling slightly in a display of curiousity about this development. "What... you want them even bigger?"
Chloe was panting as she turned towards Mary, her hands seemingly glued to the enormous new developments on her chest. "It feels so good," she moaned, a single squeeze of one mound sending such a shock of excitement up her spine that it arched for a moment. "Like all the stress is just... melting away... god, I need more..."
Never in her life had Mary seen her best friend like this - in both good and bad ways. It was a little worrying to see her so desperate, so needy for something as she was for that vial. At the same time, there was undercurrent of erotic thrill to everything she seemed to be saying and doing right now... and if it finally helped her relax, then Mary was most certainly on board.
With a shrug she rolled off her chair, taking a moment to flop herself over to the table and grab up the Breast+ vial. The pink fluid within had already refilled, the cork opening to reveal a pleasant scent wafting up to her nostrils. It was like the sweetest milk she'd ever sniffed; the mermaid briefly considered taking some herself before shaking her head, moving over to Chloe, and dumping the whole thing into her eager maw.
She gulped the stuff up as fast as she could, and almost instantly, one could perceive the results. Her already-considerable bust began to swell within her own fingers, slowly at first, stretching out with an audible strain of skin to contain all the new flesh within. Her hands moved up to grasp at stiffening nipples, her mouth now a mere perpetual outlet for moans just as her thighs were soaked with excited juices.
Mary had figured that they would stop growing at twice their previous size - that would already be comically big, so large and heave that it would impede Chloe's movement. This was not the case, as they instead continued to swell far past that imagined ceiling. It occurred to her that the vial had given Chloe a massive chest from a previously flat one; if it didn't provide a fixed amount of increase, then it must have been relative to what was there when the vial was consumed...
"Oh boy."
Thinking quickly, she stuffed the vial back into the crate and hopped back with it in hand, securing the magical liquids in case this went catastrophically wrong. Chloe seemed not to mind the enormity of the weight dangling from her chest, but the pool chair did, its cheap aluminum frame collapsing under the weight as each of her endowments reached beach ball size. Her hands could no longer even reach her nipples, instead helplessly grasping at her expanse of sensitive flesh.
Mary had to admit - there was something oddly exciting, maybe even a little arousing, at watching her friend's bust reach such ridiculous sizes. It was thrilling in an absurd sort of way, something as impossible as her own dolphin tail should have been brought to life - that something so insane was suddenly real sent this strange flush of warmth through her body. That her friend was seemingly taking so much enjoyment out of it, to the point of fluids trailing out from the cuff of her pants, certain made this easier to swallow.
Finally, the growth seemed to stop, leaving Chloe to writhe around in a mess of arousal. Though really, Chloe herself was a sideshow to what had become of her chest. Each breast was larger around than she was tall, and several times as heavy, leaving her unable to do much more than roll a bit on the spherical masses. Each nipple was easily the size of a fist, her areolas relatively small at only a basketball-equivalent width. Despite their weight, they seemed to jiggle endlessly with little provocation, as if her boobs were some kind of perpetual motion machine.
Something betwen a sigh and a moan escaped Chloe's lips, her eyes shut in contentment. "Oh god... that's good.... that's so good..."
"Glad you're enjoying it." Mary raised an eyebrow. It was an utterly bizarre sight, staring down a woman more breast than person, but it seemed to make her happy - that was good enough for her. "Do uh... do you want me to scale it back a bit, or do you just... wanna vibe like this for a while?"