Special Formula

Brooke felt one of Katarina's fingers slip inside her ass like it was nothing. It was comparable to how anal sex had felt for her before, her previous boyfriend being only slightly thicker and longer than Katarina's finger. It was soon joined by another one and Brooke moaned involuntarily at the sensation of her asshole being widened.

"You're almost ready," Katarina purred over her shoulder. "You know, I have a large syringe I could use instead of my cock..."

"Um, no no, it's ok..." Brooke replied through a slight groan.

"Oh, so you do actually want to be fucked in the ass by a huge cock then?" Katarina teased.

"Y-yes," Brooke moaned.

"Say please," Katarina teased her.

"Please!!"

Brooke felt Katarina's fist sized cock head start to apply pressure to her asshole. She could slowly feel herself starting to spread when she suddenly felt Katarina's hands grab her hips and pull her back.

"Aaaaahhhhh!!"

Brooke squealed with a mix of pain but mostly pleasure as Katarina's massive cock penetrated her ass and slipped a few inches inside. It felt like Katarina's cock was tearing her open, but the feeling was overwhelmed by the intense orgasm that started to erupt through Brooke's body, making her shake uncontrollably.

"Oh god, your ass is so damn tight!" Katarina laughed lustily.

"And your cock is so damn massive!" Brooke moaned back.

Katarina kept her grip on Brooke's non-existent hips, pulled back slightly and then pushed back in. A little more of her giant cock buried itself into Brooke's ass and so Katarina continued. With each thrust, Brooke felt her insides being rearranged to make room for Katarina. It felt like nothing she'd ever experienced in her life. She felt Katarina tug on her hair, forcing her upright. Katarina's other hand found its way to one of Brooke's enormous new breasts and started to fondle it aggressively, adding to the torrent of pleasure that Brooke was experiencing.

"This is a-amazing!" Brooke moaned.

"You've not seen anything yet," Katarina purred in her ear.

With an almighty push forward, Katarina buried the rest of her cock into Brooke who simply screamed in delight. Brooke felt Katarina grab her hand and place it on her stomach. Before she could even think about why, Brooke's mind was blown.

"I-is that?" she stammered.

"That's my cock inside you," Katarina said with a lusty grin.

With each thrust, Brooke felt Katarina's cock bulging through her stomach. Another orgasm forced its way through her, drawing moans out of Brooke that were too much for the futa to handle.

"I'm gonna cum Brooke!" Katarina moaned.

"Do it Kat, fill me with cum! Give me a big fat ass!!" Brooke squealed in return.

To her surprised delight, Brooke could feel Katarina's cum as it jettisoned out of her and into her ass. Just like with her mouth, it kept going and going but this time Brooke's hand's were in exactly the right place to feel what was happening. Her stomach bloated and stretched beneath her hands, pushed outwards by the sheer force and volume of Katarina's orgasm. She started to see past her engorged breasts what could easily be mistaken for a pregnancy bump as Katarina's cock slowly began to stop releasing its seed into her.

"I'll need to keep my cock inside you until the change happens, don't want any of that cum pouring out do we?" Katarina told her.

"No... we don't," Brooke panted. "Oh, oh I can feel it happening!"

As before Brooke's stomach started to shrink and she felt the sensation from her chest localised to her ass, hips and thighs.

"This is always my favourite part," Katarina laughed lustily but Brooke was barely listening.

She was instead focused on the pleasure of her transformation. She could feel herself widening, her stick thin thighs plumping into thick tree trunks, her hips quickly surpassing the width of her shoulders and most importantly her ass ballooning to such a size that the cheeks were pushing Katarina back whilst enveloping her cock at the same time. When it finally stopped, she had the big fat ass she'd asked for and then some.

"Damn, that's an ass I wouldn't mind fucking again," Katarina laughed, laying a hefty smack on one of Brooke's newly engorged ass cheeks that sent a lightning bolt through Brooke and made her ass wobble in ways she'd never experienced before.

"I would love that," she started, "but I think that any more of your cock and I might be ruined for life!"

Katarina cackled.

"True, true," she said.

She pulled out of Brooke, Brooke still feeling every inch as she did, and stepped away to admire her work. Brooke stood after a moment of getting her bearings back and started to look and feel around her new body.

"Oh my god!" she said delightedly. "You've made me a perfect 10!"

"It's what I do," Katarina grinned.

"I can't even begin to thank you for this," Brooke beamed at her.

"Your thanks are appreciated but payment will do just fine too," Katarina laughed.

"Oh, of course," Brooke giggled in return.

She started to walk towards her bag, a harder task than before as parts of her that never normally touched were now wobbling all over the place, and noticed that somehow Katarina was still hard.

"Does that thing ever go down again?" she asked.

"Only once I'm fully drained really," Katarina replied off-handedly.

As Brooke reached into her bag, a thought suddenly crossed her mind.

"Kat, can I ask you something?"

"Go ahead."

"So if your cum is swallowed, bigger boobs. If it's taken in the ass, bigger ass. What happens if you cum in a girl's pussy?"

Katarina seemed to be in thought for a moment before her familiar grin formed back on her face.

"Would you like to find ou..."

"Yes," Brooke said, with zero hesitation.

Katarina turned and swiped her desk clear before lying down across it, her cock standing to attention like a phone mast. Brooke understood without instruction and immediately went to mount Katarina, finding she'd have to kneel right up first in order to try and guide her in. She reached between her legs and grabbed Katarina's cock, rubbing the head against her pussy before beginning to push down. Her pussy was still soaked from her multiple orgasms and so the cock slipped inside her far easier than with her asshole. She moaned as it entered, relishing the feeling of fullness in her pussy she had not long experienced in her ass.

"God, my pussy has never been so full!" she moaned.

Katarina reached up and grabbed one of Brooke's breasts, bringing it to her mouth and gently biting down on the nipple, making Brooke yelp with surprised delight and descend even further down onto her cock. Brooke started with a steady motion, revelling at how she could feel the weight of her ass travel up and down with her. It wasn't long before she could feel Katarina's cock hitting her back wall. She tried to wiggle down a little more on her, but she wasn't budging.

"Hey, don't worry," Katarina said with a grin, "you can't go as deep in a pussy anyway, and holy crap yours feels so damn good!"

"But if you could get more in, that'd be better for you and you'd cum more right?" Brooke asked.

"Well yes but..."

Before Katarina could finish, Brooke had lifted her hips and slammed the full extent of her new weight down. The two screamed in unison as Katarina's cock broke through Brooke's back wall into her womb and her pussy swallowed the rest of Katarina's cock, the head bulging beneath her stomach as before.

"Oh my goooood!!" Katarina cried.

"Oh yes!!" wailed Brooke as she started to forcefully bounce up and down on Katarina, drilling her cock back inside her each time.

"I'm gonna cum, you're making me cum!" Katarina moaned in ecstasy.

Brooke sat up, making sure her full weight was atop Katarina's cock to get it as deep as possible and smiled deliriously as she felt the futa start to cum inside her. The bulging head was soon lost as her stomach started to bloat once again in a feeling she'd quickly come to adore. Each throb of Katarina's cock brought with it even more of her amazing cum and Brooke was happy to stay where she was until all of it had filled her pussy and womb to breaking.

Finally she felt Katarina go slightly limp beneath her, laying panting. Brooke looked down on her with satisfaction, rubbing her bump as she did.

"That was in-fucking-credible," Katarina laughed.

"So, what now?" Brooke asked eagerly.

"Wait and see," Katarina replied with a grin.

Brooke started to feel the bump beneath her hands shrinking down and waited in anticipation to see what part of her would grow next. But instead, her bump kept shrinking and nothing else happened. She sat confused as her bump all but disappeared with no other effect.

"I-I don't understand," she said, both confused and disappointed.

"You will in a moment," Katarina smiled.

Brooke suddenly felt the strange sensation she'd come to love just above her pussy. Her eyes immediately went downwards and once again her jaw dropped. Starting to protrude from her body were a currently small cock and balls that were swiftly and steadily growing in size.

"What the f... oh, oh god that feels so..." she trailed off with a moan.

Katarina simply laid back and enjoyed the view. Much like her breasts and ass before them, Brooke's cock was rapidly making its way from normal, to big, to insane in size and just kept going. Katarina kept expecting to see it stop, her smile changing to an awed look of shock as Brooke's cock quickly surpassed her own in both length and girth and just kept going.

"Oh... my..." she said trailing off.

Now apparently fully grown, Brooke's cock stood at what must have easily been two feet long and twice the girth of Katarina's with two baseball sized balls beneath it.

"S-so that's what it does," Brooke panted.