"I think I'm gonna go with the potions again!"
"That's what we like to hear! Keeping that point train a-rolling!" Eric cheered. The audience celebrated as Kirsty accepted the new tincture from the attendant. She skimmed through the instructions before going over to Mary.
"Here, you're supposed to drink this."
"O-oh, alright. Um, thank you." Mary took the jar from Kirsty, eyeing it nervously as she popped the lid off. She brought the glass vial to her lips, tilting it back and quickly swallowing all of its contents. Before she could even set the bottle down, an odd tingling feeling spread through her breasts, and Mary brought her hands up to them in response, cupping them from below. She let out a gasp as her nipples suddenly swelled and stiffened incredibly, swelling from being the width of her pinky to that of her thumb in a split second. The jumbo screen above the stage gave a glorious close up of one of Mary's bolstered teats, showing off every adorable detail on it, as well as documenting the first few droplets of milk that started to drip from it.
"O-oh my!" Mary said, somehow blushing even harder. Her nipples throbbed lightly with her heartbeat, growing a little bit bigger with each twitch. Her areola grew a bit too, radiating out to cover about half an inch more of each breast. After half a minute of slow growth her nipples seemed to have settled on a size, now each about 3/4 of an inch in diameter. Mary's hands hovered a few inches away from her breasts, seemingly conflicted between the feeling of her nipples demanding stimulation and her being too shy to fondle herself in front of an audience.
"Here, let me help you out with those." Kirsty nudged Mary's arms aside, bringing her head down and wrapping her lips around the girl's left nipple. This time there was no gradual buildup of milk- with the first suck Kirsty gave, delicious and warm milky essence readily flowed into Kirsty's mouth, which she happily swallowed, hungrily sucking for more. Whatever the tincture had done, it was making milk much faster than Julie's natural lactation. The stuff was a different taste than Julie's had been as well, a bit sweeter, but more subdued of a taste overall. Kirsty filled her mouth with as much as she could hold before greedily gulping it down.
Mary moaned in lurid satisfaction as Kirsty sucked on her aching teat. Either forgetting or no longer caring about the audience, she brought a hand down and slid several fingers between her pussy's lips, vigorously rubbing her rosy pink folds. The crowd whistled wildly.
As Kirsty drank, a pair of bumps started to form halfway down her abdomen, in she shadow of her newly big and milky tits. The crowd whistled and cheered as the screen depicted the slowly growing mounds, as well as the next shot of Mary's slowly shrinking one.
Kirsty moaned into Mary's chest as she felt a tingle in her burgeoning second rack. The tips of her now B-cup mounds took on a rosy pink color instead of the tannish-white around it, before a pair of nipples popped up from the spots, areolas radiating out from them to meet the size of the pink pigmentation. A few swallows later, both girls felt the flow from Mary's chest begin to waver, soon dwindling to a thin stream, then just a few drops, all while Kirsty continued suck, to nurse out as much as she could. Once Kirsty was satisfied that Mary's breast was dry, she released the volunteer's nipple, pulling her head back to find that where Mary's left breast had been minutes ago, it was now entirely, boyishly flat. Her left nipple and areola had also shrunk, now much smaller than even before she drank the potion, a more fittingly boyish size on her lack of a breast.
"Don't stop now!" Eric cheered. "You're only halfway done! Unless of course you'd be so cruel as to leave poor Mary half-titted like this?"
"Eep!" Mary cried out. "She wouldn't do that! C'mon Kirsty, drink up!" Mary jiggled her remaining breast nervously and invitingly, getting droplets of milk all over in the process. Kirsty grinned and brought her head back down, popping Mary's other nipple into her mouth.
Kirsty's two newest tits promptly resumed growing as she began drinking from Mary's shrinking breast. The taste had really grown on her, and Kirsty soon found herself gulping down mouthful after mouthful nearly as quickly as she could. She could feel her donor's nipple slowly thinning out between her lips, and eventually she could feel the lack of cushion between her face and Mary's chest as the girl's milk supply began to dwindle. Even after the flow stopped completely, Kirsty sucked a few more times. She wanted to make sure she had drunk every drop of her wonderful new tits. Satisfied that she had, Kirsty popped Mary's nipple out of her mouth.
As Kirsty went to straighten back up, she staggered forward, waving her arms to keep her balance, and unintentionally jiggling all 4 tits quite a bit in the process, much to the audience's excitement.
"Whoa there! You alright?" Eric said, offering a hand as Tanya stifled a chuckle.
"Yeah, sorry!" Kirsty said, straightening up fully. "I'm a good bit more top- and front-heavy than I was when I came down, I guess it'll take some time to get used to it!"
Now that they had a moment, both girls looked down and squealed in excitement as they checked out their new forms. Mary was now flat as a board with petite nipples to match, with her old perky C-cup rack now resting on Kirsten. Mary ran her hands down her smooth front, marveling at being able to do so.
Conversely, Kirsty reached out and cupped her new third and fourth tits from below, giggling as she bounced them around. Despite her extra pair being a couple cup sizes smaller than what they were under, it didn't look bad on her. The nipples she grew on her lower pair had grown to match the size of the ones on her upper pair perfectly, which helped tie her look together. She gave her new assets a soft squeeze, and moaned in pleasure and surprise as milk flowed out of them onto the floor below.
"Hey what happened?" Kirsty asked her hosts. "I thought Mary said she didn't lactate?"
"Hm? Oh, it's because you yourself are lactating hon, it's not just the tits you got." Tanya explained. "Julie and you didn't just swap tits, you swapped whether or not you were lactating, independent from the tits. Now she doesn't and you do. That means you can look forward to any and all breasts you have being milk factories."
"Gosh." Kirsty pondered her tits for a moment, then gave them another squeeze, moaning as fresh milk dribbled onto the stage. She quickly got lost in the feeling, alternating between all four of her tits, kneading out the warm and plentiful liquid with scattered moans.
In the meantime, Mary had started re-dressing herself, now covered from the waist down. She bent down, picking her tank top up off the ground and putting it on, finding that it didn't quite fit the same without her tits filling it out. The low neckline that once showed off Mary's cleavage now instead completely exposed her nipples, as well as several inches of chest below them. Mary seemingly couldn't care less though, scampering back up to her seat while beaming, her nipples still bared to the world.
"Whew, as much as the audience, and myself, are enjoying the view, we're gonna need you to come back down to Earth Kirsty."
Tanya's prompting snapped Kirsty out of her milky massage, leading her to bring her hands back down and chuckle sheepishly at the puddle that had accumulated on the stage beneath her.
"Well folks, you all saw how much she's enjoying herself, you better believe she's still up for anything!" Eric announced. "Now who's gonna be our next lucky volunteer?"