Sleepover time!

Liz shook her head, "I should really get that homework done, and since we're all here, why not have a sleepover!" She then sent a meaningful glance down to Athena, "A normal one, perv." Athena simply smiled innocently while Alicia clapped her hands while bouncing, her heavy body causing audible thuds to be heard.

"Yay! It's been years since we had a sleepover Liz!" She rushed over to her bag and then paused, "Damn, how the heck a I going to fit in these?"

Athena shrugged her massive shoulders, "Eh, so it's a naked slumber party. So where's your homework, I might as well see what I'm up against." Liz nodded and showed her the homework assigned to her, prompting a grimace from Athena, "Yeah, I figured as much." Stretching her huge arms, Athena walked towards the bathroom, "I'm going to get cleaned up, try and figure out one of the problems and we'll go over it when I'm done."

Liz nodded and grabbed her pens and pencils as Alicia shouted, "I'm next after you!" The bulkier girl had found a tissue box and was busy cleaning all the cum out of the deep crevices in her abdomen, tossing them into the wastebasket before sitting cross-legged next to Liz, "Geez, ever since you got that dick, you've been getting huge!"

Liz blushed, "I've also been getting pretty horny as well, but what I don't get is why you two got big. I mean, I can understand me, Josh and me went to our doctor and it's some kind of really rare genetic condition, but why would it make you two grow?" She focused back on the problem she had chosen, "Fuck, this is hard. You know anything Alicia?"

The bulky girl looked at the problems and whistled softly as she took another tissue and **** it deep in an abdominal crevice to get at some leftover cum, "I know a few things. Try doing this..."

And so the two friends began going over the problems while in the shower, Athena was inspecting not just her muscles, but her thick nipples, watching as they slowly receded back into her collapsed aereolas. Curious, she shoved a pair of fingers into the crack and began stroking them, gasping slightly as she felt the swell inside and push forward until they peeked out, dribbling milk, but Athena kept stroking until with a sharp gasp she felt her nipples pulse as milk squirted out in a pulsing gush of white liquid.

Staring at her pulsing, swollen nipples, Athena licked her lips before shaking her head and focusing on getting cleaned up while feeling them slowly shrink back to normal. She considered the fun that could be had in the future, but for now, she started washing her hair.

After several minutes, with a towel wrapped around her head, Athena walked out of the bathroom, "All yours shrimp."

Alicia growled lightly and deliberately bumped into Athena as she passed by, prompting a smirk as she sat down next to Liz, "Cute, I like her. Hard to believe she's such a wall-flower in school"

Liz nodded, "Alicia tends to lock up around strangers, but when she relaxes, she's actually pretty aggressive. She surprised me when we were friends, because I found out that the shy girl actually is really aggressive when playing with her friends." She rubbed her arm, "Got a few bruises from her before all this happened."

Athena giggled, "Well, I'm not the one who's going to puberty overdrive." Her expression became serious as she looked over Liz's coursework, "Not bad, your friend help you?" At Liz's nod, Athena smiled, "Okay, this is a good start, but here's a way to make things get worked out much easier..."

As the older girl began running through the tricks she learned with Liz, Alicia sighed in relief as she finally managed to get rid of the slimy feeling on her abs, running a hand down the stone-hard muscles, Alicia flexed and watched the surge forward, before she posed with her arms like she had seen in a few comic books and cartoons, watching her massive biceps swell. Giggling under the stream of water, Alicia tried to flex her pectoral muscles and her eyes widened as they swelled outwards, pushing her large breasts out in the process.

Looking down at the firm flesh, Alicia noticed the way her nipples had swelled slightly and licked her lips as she wondered if they could...she began stroking and tweaking her nipples, giggling as she felt them swell larger and large until, "Ah!" Streams of milk squirted out of her nipples and she eagerly started sucking her own tits.

As the squirts subsided and her nipples shrank, Alicia quickly made sure everything was clean before exiting the shower. As she walked out with a towel over her shoulders, she found Liz and Athena hard at work on Liz's homework and sat down next to Athena to see what she was teaching Liz.

Liz smiled at her friend, "Oh, Alicia! Think you can help Athena with her biology?" The bulkier girl nodded and before long a study session was now underway.

Downstairs, Josh heard the laughter and thuds from upstairs as he prepared some snacks and for a moment his mind drifted to his little sister...well, little in terms of age now, engaged in all kinds of sleepover activities, before his mind then reminded him that she was now massively muscular with an equally huge dick between her legs.

Josh groaned and looked down at his pants, "Shit. Keep it together Josh, you are not going to try and have sex with your sister." He quickly made sure everything was ready and headed upstairs, hearing the laughter coming from Liz's room, and with a check to make sure he wasn't tenting his pants, he knocked on the door, "Liz, it's me, I got snacks for you and your friends." There was another round of giggles before a laugh heralded a series of soft thumps before Liz opened the door.

"Thanks Josh!" Liz declared as Josh saw his sister at the door naked as the day she was born, and she had gotten taller and bigger as her soft twelve-inch penis swung freely while she took the tray of snacks, and he caught a glimpse of the other two girls.

He recognized Liz's best friend Alicia only by her face as she shifted her massively bulky body while engaged in arm-wrestling the blonde, Athena, who had also gotten bulkier. Liz noticed his stare and blushed, "We, uh, had a little experiment before we started the sleepover."

Josh nodded, "So long as you don't go overboard Liz." Liz smiled and leaned down, just enough that Josh felt her long nipples brush against his shirt.

"Aw, is little Josh jealous he doesn't get to play with the girls?" She teased and Josh flushed slightly before turning away, trying to play it cool.

"You have fun with your girl games Liz." He heard her giggle before the door closed and he decided to go to his room.

Fuck it. He wasn't going to fuck her, but he wasn't so stony that he could resist jacking off to her. He walked into his room and unzipped his pants, letting his eight-inch penis stand upright and erect.

"Fuck me, I can't believe I'm getting turned on by my sister."

Finally, the sleepover eventually to the sleep part and the three massive girls were sharing spare mattresses. Athena and Alicia had found that the effect of drinking Liz's cum eventually wore off and they shrank down, but only by half. So now they were only five times as bulky before they drank the cum, and now their clothes fit, although they were tight fits.

Still, as Liz felt them shift close enough to hug her, she smiled. Things were finally looking up for her, and she hoped it would continue.

The next morning, after Athena explained her home situation over breakfast and Liz's mother agreed to get the spare room ready for her to stay over for a while, Alicia asked, "So, how should we check that these," she flexed a bicep, "aren't just for show?"

Liz looked thoughtful, "Hmm..."