Krystal finished pulling up her thong, the red string sliding between her cheeks. Little did she know she had also loaded a little passenger into her caboose. She bent over again, and grabbed the hips of her gym shorts, and began to pull them up, fitting them snugly around her own curvy hips. As she let go of the elastic waistband, a sharp snap could be heard as the band sealed around her hips. Krystal plopped her butt down on the edge of the bed, and began to lace up her shoes.

********

Sara kept slipping deeper into Krystal's crack. Her bending over to pickup her shorts had spread her cheeks, turning the thong into a silky slide that Sara was riding. She rolled over and clawed her fingers at the fibers, but only managed to slow her descent. Suddenly, Krystal stood upright again, and the walls of warm flesh closed in on Sara and engulfed her again. This time, Sara was pinned facing outwards with her elbows bent, her hands pressed against her cheeks, and her face pressed into the crimson fabric. Her nose couldn't suck in enough air through the thin gaps between the fabric, so Sara opened her mouth and tried to gulp in a lungful of air. The air filtered through the thong, picking up a sour odor, making Sara gag on her first few breaths. She could taste the dried sweat moistening against her open lips, and fought the instinctive urge not to lick her lips to re-wet them, knowing the resulting taste would be unpleasant at best. After a few breaths, her nose and lungs were becoming accustomed to the sweat tainted air, and she began to try and wiggle her arms above her head. "Maybe," she thought, "I can pull myself up along the thong, and try and escape." Little did Sara realize that even if she managed to pull herself up Krystal's ass crack, the imposing gym shorts had sealed the top of the thong shut with it's elastic. and would prove too powerful for her to break free.

Sara felt the thong begin to stretch again, but it wasn't tilting. She was confused at first, until she realized that Krystal must be sitting down! "No no no!" Sara wailed, when suddenly the cheeks around her compressed further, and squeezed Sara firmly into the flesh. Sara pushed her hand out with all her might, just to create a tiny gap to breathe. She hoped Krystal didn't sit long, she wasn't sure how long her little arms could hold the mountain of ass back.

********

Krystal finished lacing her shoes, then hopped up and skipped downstairs. Jeanne was waiting for her in the kitchen, and had laid out a pair of water bottles and granola bars on the counter; fuel for their ride.

"So, Krys, feeling up for a challenge today, or want to stick to the streets?" Jeanne asked, hoping to prod her sister into a harder ride today. Had Jeanne known that Krystal had a little stowaway in her rump, she would've pushed her even more for a long hard ride.

Krystal grabbed one of the bottles from the counter, and cracked the plastic cap loose. "You pick, sis. I'll go easy on you whatever you pick." She smirked and took a sip of ice cold water.

"Hey, might want to save that for the ride, you'll need it," Jeanne shot back, tossing one of the granola bars at Krystal. It bounced off her boob, and landed on the floor with a crackle.

"Oh, it's on!" Krystal shouted, quickly replacing the lid on her bottle, and grabbing the other bar from the counter, leaving Jeanne to pick up her own from the floor. She scooted around Jeanne, and headed for the garage. Hitting the garage button by the door, Krystal strapped on her bright pink helmet as light started to our in under the door. A cartoon skull and crossbones adorned each side of the helmet, with the words "bad girl" written below in bold black lettering. As she latched the strap under her chin, Jeanne walked into the garage, already snacking on her granola bar.

"Thought you said to save it for the ride. What, you need a pick-me-up already?" Krystal snickered.

"Nah, didn't want you stealing it when I pass you," Jeanne replied, as she snapped her helmet on. Her helmet was a neon green, with the same skull stickers as Krystal, minus the lettering. They both pushed their bikes out of the garage, and closed the door behind them.

"Okay, you said a challenge. What did you have in mind?" Krystal asked.

"I'm thinking a trip down memory lane. Remember the pier we got drunk at last year? I'll race you to it," Jeanne smiled at the memory. Krystal had turned 21 last year, and they went on a drinking spree that night to celebrate. Neither of them remember much, only the morning after when they both woke up under one of the local beach pier. Krystal wasn't very good at holding her liquor, and had never quite gotten over passing our on her first night of drinking.

"Oh, you just HAD to pick that spot," Krystal rolled her eyes. "Fine, and loser buys lunch. You'd better have your wallet, Jeanne!"

Jeanne smiled, and patted her front pocket. Krystal did the same, nodding to her sister.

"On your marks... get set... go!" Jeanne yelled.

The sisters pushed off, standing and pressing down on the pedals. As she picked up speed, she pressed herself, feeling the early morning sun already starting to heat up her skin.

********

Sara squirmed in her fleshy prison. Every step Krystal took had shaken her a little deeper into her ass, and Sara was losing a battle with the thong. She couldn't make out everything that was being said, but she did catch the countdown from Jeanne. As Sara heard go, everything started moving moving faster. The cheeks rose and fell against her, rubbing her back and forth with each pedal push from Krystal. Sara was smushed from both sides, being rolled slightly with each movement. She tried to keep herself facing outwards, but was having difficulty. She soon found herself turned sideways, her head held firmly by the soft skin. Her right arm was completely immobile, squished deeper in Krystal's ass. Sara reached with her left hand, clinging desperately to the thong, trying not to be sucked in further. Suddenly, the thong lurched forward, smashing into Sara and pulling her deeper. Sara squirmed and screamed, vainly trying to fight off the huge panties.

********

A few minutes into her ride, Krystal started to feel a wedgie forming in her crack. Reaching back with one hand, she firmly tugged up on her thong and shorts, wedging them both into her ass. She figured she might as well not fight against her own ass, and just let it have it's meal of silk and spandex. As her hand returned to the handle bars, Krystal shifted into higher gear, and lowered her ass down onto the seat for the first time. Her cheeks split on the thin seat cushion, allowing it to press deep into her ass crack. Krystal kept pedaling, determined to beat her sister.

********

Sara was in what could only be described as a nightmare. Krystal had yanked her thong deep into her ass, unknowingly shoving her little passenger deeper in the process. Sara was now facing into the dark crack, and the smell was much worse. The humidity was also rising, turning the ass into a giant sauna. Sara's eyes darted around, unable to turn her head even a little. As her eyes looked upwards, she stared at several beads of sweat forming. One by one, they became larger, and began their journey down Krystal's ass. Sara breathed deep, and held her breath as the first drop rolled straight into her face. She pressed her lips tightly together, trying hard to keep the salty liquid out of her mouth. Her hair was instantly soaked, and clung to her face. As the drop rolled down her body, it systematically soaked her shirt, then her shorts , and finally her socks and shoes. Sara sputtered, spitting the remaining sweat from her lips. She looked down, and watched as the droplet soaked into the thong near her feet. While she looked down, another droplet collided with her hair, quickly surrounding her face before she had a chance to react. It quickly worked its way into her mouth, filing it with briny water. Sara's eyes bugged out at the horrid taste, but there was too much sweat around her to spit it out. She gagged twice before the droplet had rolled on and released her face, finally letting her spit out the salty sweat. Sara's spirit was breaking, how could things get any worse?

********

Krystal looked over at Jeanne, then smirked and swerved down an alley. Jeanne yelled some obscenity after her, but Krystal was already too far away to make out what she said. Krystal knew more of the back roads and shortcut in Los Angeles than Jeanne did, and she intended to use every advantage she had.

The ground in the alley wasn't paved smooth like the streets, and Krystal swerved every few seconds to skip the potholes. Some were too big or close together for her to avoid, however, and Krystal hit a few head on. Each pothole she hit jarred Krystal and her bike, her chest and ass bouncing with each bump.

********

Sara felt everything fly up, then come crashing back down. Krystal must've hit a bump. The sweat had made everything slick, and the bump had shaken Sara loose enough that she began to slide down the thong again. Each bump she slid a few feet, getting closer to Krystal's asshole. Sara fought against the meaty walls, but they simply responded by raining down more sweat onto her. The air was very humid, like a jungle, and the vinegary odor of sweat began to mix with the foul odor of shit as Sara slid further. The thong was too slippery now for Sara to grab, so she tried to brace herself against the ass cheeks, like some cosmic hero in a trash compactor. One last bump, and Sara slid down several feet, coming face to face with Krystal's asshole. Sara wretched at the smell, it was beyond revolting. She could hardly turn her head away, the massive cheeks held her captive. In front of her, the pink ring swayed back and forth in time with Krystal's pedaling. Sweat beaded up around it, slowly dripping its way down to Sara. She tried to move her arms to defend herself from the salty onslaught, but it was no use. The droplets morphed around her arms, and soaked her face in foul anal sweat. Sara screamed in disgust, shaking her head back and forth as far as the ass cheeks would allow. The sweat continued to pour down, drop after drop drenching her whole body.

Sara felt something firm against her back. It wasn't just the thong, something more substantive was pressing into her. Sara wailed as the firm pressure moved her slowly forward, closer to the awaiting asshole. It twitched as her face was now inches from the puckered opening. Sara tried to hold her breath as much as she could; the smell was overwhelming. Her legs were pressed into the skin below the asshole, unable to budge at all with Krystal's weight resting on them. As Sara took another breath of foul air, the asshole lunged forward, her face making contact with the tight hole. Sara's struggles increased, as her air supply was cut off completely.

********

Krystal slowed, and came to a stop at a red light. She leaned back in her seat slightly, resting her weight completely on her ass. As she waited for the light to change, she saw among the cars another biker. Jeanne flew through the intersection, turning her head in Krystal's direction as she passed. Krystal could've sworn she saw Jeanne smiling as she sailed past. Grunting in frustration, Krystal began tapping her foot on the pedal, impatiently waiting for the light to change. The instant it changed, Krystal stood up and threw all of her weight into the pedals, trying to keep pace with the cars around her, and make up time and overtake Jeanne.

********

Sara gasped as the asshole retreated. Her face was coated in a greasy film from the foul orifice. She coughed a few times, and struggled to wipe the residue from her mouth. The sweat continued to rain down one drop at a time, this time providing her with a rinse of relatively clean water. Sara tried to spit out the taste of ass from her mouth, only to have it replaced immediately with the salty flavor of sweat. As the asshole lifted, the cheeks began their rhythmic pumping up and down, and resumed kneading Sara in between. Her legs were plastered to the thong and Krystal's skin, and as Sara tried to kick them, she realized they weren't going anywhere. Her arms were freed up slightly though, and Sara tried to keep the sweat out of her mouth and eyes, and hope that Krystal reached her destination soon.

The cheeks slowed their churning, then stopped. Sara knew what was coming, and pushed her arms out in front of her face, hoping in vain to stop what was coming next. Sure enough, the pink ring descended on her, and her fingers slipped against the oily surface, offering little resistance before getting pressed back above Sara's head. Her face was once again buried against Krystal's asshole, and her muffled screams barely registered outside of the thong, and were drowned out long before they could reach anybody's ears. Sara beat her fists against the edge of the asshole, pleading for clean air.

********

Krystal came to a stop at another light, resting her legs and taking several deep breaths. She hadn't seen Jeanne again, and hoped she was stuck in traffic on another street. As she waited, she felt a small itching sensation in her ass. Looking around at the other drivers, she made sure the coast was clear before reaching back and rubbing her finger against her sweat-soaked shorts. The itch was right against her asshole, and Krystal tried not to draw too much attention as she rubber her finger back and forth to relieve the irritation.

A horn beeped behind her, and Krystal jumped and nearly fell off her bike. The light had changed, and the older lady behind her was quite finished with the show. Krystal felt her face flush cherry red, as she straightened back up and pedaled through the intersection.

********

Sara was pounding her fists against the asshole when something unexpected pushed against her from behind. Apparently she had gotten Krystal's attention, but not in the way she had hoped. Through sopping wet thong and shorts, a massive digit pressed into the back of Sara's head, and began to rub up and down. Sara's head was pushed hard against the puckering hole, which slowly opened and slid along her face, stopping at her neck. Sara writhed in absolute disgust, pushing with all her might to pull her head free. The more she struggled, the more vigorously the giant finger rubbed. Sara fought against her own will, and managed to hold still for several seconds, waiting for the finger to retreat. As it did, Sara gave one final push with her hands, and her head slid free with a slick popping sound. Her hair was now also coated in an oily film, and her arms and chest were coated as well. Sara sobbed, she was nothing more than an itch in someone's ass.

********

Krystal caught all of the green lights the rest of the way. As she rode onto the sidewalk, she looked ahead and frowned. Riding out onto the pier was a biker with a neon green helmet, it had to be Jeanne. Krystal grumbled, knowing Jeanne wouldn't pick the cheapest place to eat if she won.

As she rode up to the pier, she noticed the green bike helmet had stopped halfway out. As she got closer, her hopes lifted; the cyclist was a man, not Jeanne! Krystal pedaled past him, heading out to the edge of the pier. As she reached the end, she dismounted her bike and leaned it against the railing, and pulled out her phone. Her thumbs tapped across the screen, sending a quick text to Jeanne to see if she had arrived. Krystal held the phone up, and snapped a quick picture of herself and her bike, as proof she was there. She pressed the green Send icon, and slipped her phone back into her pocket, waiting for the buzzing to announce Jeanne's reply. She turned around and faced out towards the sea, enjoying the cool sea breeze on her face.

********

Sara was exhausted. The giant cheeks had finally stopped pedaling, and were now spread just enough for her to move around, albeit slowly. She didn't have nearly enough energy now to try and climb her way out, she'd just have to wait until Krystal changed, or stopped abusing her with her ass long enough to rest. Sara laid back in the thong, and quickly passed out from exhaustion.