The giantess pulled down her leggings and panties both in one go, bending her perfectly round buttocks over the toilet. Mark could feel her anus gurgling around his face, ready to release the foul mess of feces within. A booming impact struck through Sarah's ass like thunder as soon as her butt made contact with the seat. The cool seat dug into the fat of her ass cheeks, squishing nicely but also pushing them together. Sarah wiggled her hips back and forth, getting comfortable and spreading her glorious ass so the poop would come out cleanly.
Light and fresh air finally made its way to Mark. His head was still wedged firm inside her asshole, and his chest was crammed against the sticky oils running down the line of her ass crack, but despite this he could feel the chilling breeze of toilet air on his sweaty back. Sarah's ass crack was laid bare to the inside of the bowl, her sweaty crotch wafted its stuffy scent outwards and dispersed it above the water. The drop was several stories high for Mark, and one he knew he'd be making in a few moments. The girl's anus gradually became more active around his head, pulsating in and out as it readied itself to release her load. The rancid smell and heat coming from within was extremely close, and from the way her muscles were twitching, it didn't seem like it could be held back much longer.
Still feeling sluggish from her orgasm, Sarah was intent on just letting her butt do its thing while she sat there. Her thoughts were in a cloud of leftover sexual fantasies, reflecting on the videos she had been watching with her phone just minutes ago. Just then her anus twitched and a sharp pang of discomfort brought her back to reality. Apparently she hadn't been drinking enough water, and her poop was too thick to slip out her ass on its own. The teen let out a sigh and pushed with her muscles, flexing her sphincter until the turd broke through.
As Sarah's shithole opened Mark felt the vicegrip on his head retreat, giving him clearance to breathe again. Light spilled into the darkness of the giant hole, revealing a wall of solid gunk just an inch away from touching his nose. The heat coming off of it roasted his face, and the concentrated intensity of its smell burned his lips. Sarah's wrinkled anal muscles contorted around the turd, pulsating and struggling to push it out. She must have been backed up for a while, the width of this log was so thick that her asshole was having trouble opening wide enough for it. Mark hung on to the rubbery filth-encrusted rim as it gaped more and more around the shit, marveling at the magnificent size of his crush's poop. Sarah was a petite girl, but even for a normal person this turd was enormous. Up above her voice let out a grunt, and finally her ass squeezed hard enough for the head of her bowel movement to peek out the exit.
"Nnnngh!"
The giant brown bundle of sludge came out her sphincter slowly, first appearing like a rounded ball until it grew into a thick pillar. Wet crinkles came from her ass as it pushed the solid load along, easing it out little by little. Mark was taken aback by the rancid stench, he loved the smell of her farts but the concentration of raw shit stink was proving to be too much even for him. He hacked and spit, trying to hold on to her anus as it gaped but could feel himself slipping. Sarah's asshole was pushing into a dome-like shape as she expelled her waste, becoming smoother against the grip of Mark's hands and peeling the sticky slime that was holding his upper body in place off his chest. One twitch of the girls anal maw was all it took, her farthole clenching slightly around her crap was enough to knock Mark completely off her body.
The young man entered free-fall, colliding with the side of his friends extended turd, smearing shit along the side of his body before dropping all the way into the pool below. He hit the water with a small splash, plunging several feet deep into the clear liquid. The toilet bowl was massive compared to him, easily larger than any swimming pool he had ever swam in before. Grossed out by the warm smear of shit that had slathered the side of his body, Mark started to rub it off his skin with his hands, using the water he was swimming in the clean it off. Relatively it was a small amount compared to hers, but some of the larger clumps on his shoulder and hips were big enough to be full-fledged logs of his own.
Preoccupied with making himself clean, Mark didn't notice the real danger he was in until it cast a dark shadow over his head. He looked up, only to find Sarah's huge hulking log of crap dangling just a couple feet overhead. It was massive, even greater in size than a full transport truck, and suspended directly above his body. A look a pure shock fell across Mark's face, and his hands slowly stopped scrubbing his shoulder.
"...Oh. FUCK-!!!"
Sarah's ass let the shit out completely, finally unplugging itself from the puckered asshole up above. Like a train crash it steamrolled the tiny man straight into the water and then plunged itself to the bottom of the bowl. Buckling under its own weight the crap broke apart into several thick pieces, still lengthy enough to be considered normal shits on their own. The displacement of such a large object into the water created a humongous splash, and explosion of water that carried rippling waves across the bowl. Mark had to separate himself from the end of the descending log quickly, or else face an early grave at the very bottom of the bowl. Powerful waves pushed at his back as the shit dove deeper, forcing his tiny body into becoming one with the girl's poop, but he wouldn't have it. Using the strength of the current he managed to roll his body sideways, finally breaking free of the mass of waste and swimming freely again. On his way back up he had to avoid the other falling pieces, as they too sank into the abyss.
With a loud gasp he broke the surface of the water, barely avoiding death. He looked back up at Sarah's asshole, the incredibly sexy orifice that he had been cozying up to all day had almost killed him. Despite this, part of him still felt an overwhelming sense of lust towards it, and wanted to get back up in its crevices as soon as possible. Even the girl literally shitting on him wouldn't be enough to stop his fetish for her raunchy asshole. As if on cue Sarah let out a big sigh, once much louder than Mark's little pants for air. Her breath of relief sounded great, almost sexual even, from such a huge mass of excrement leaving her giant body. The dump was mostly submerged at this point but it made the air around Mark stink. With her anal muscles relaxed the giantess leaned back into the toilet seat. Her asshole puckered up above, and unleashed a gargantuan fart into the toilet.
Free from the confines of her panties, Sarah's asshole let out a bellowing explosion of gas, as if it boasting how loud it could really be. The girls butt shook the entire bowl, creating ripples in the water that were only smashed against the other waves formed by the gusty stream of anal air. Mark watched as hot mucus spat out his friends shithole as it farted, splattering into the waves right next to him. The smell was ripe and spicy, clearly an after effect of the meaty burrito she ate earlier. By the time it was done the toilet bowl had become as hot box of foul noxious gas, kept trapped inside by Sarah's juicy thighs and butt cheeks.
That's when the rain started. The floodgates of Sarah's crotch broke loose, finally bursting with a heavy stream of pee that stained the water a yellow hue. The temperature got warmer around Mark and the smell because a mixture of the girls salty stinging piss and her pungent anal fumes. The spray was concentrated near the front of the bowl, but stray droplets of liquid fell upon the tiny students head. There was nowhere for him to be clean anymore. Sarah had really been holding back, her stream was lasting for a long amount of time, indicating how full her bladder was.
The force of pee poured into the toilet like a waterfall, creating a bubbly fizz that crawled towards Mark. Sarah's asshole belted out another small fart, and then a second turd peeked out from her gaping anus. One by one her ass started to drop bombs of shit from above. They nearly hit the tiny man a second time, but still caused gigantic explosions of piss-filled water around him. Mark felt like he was in the middle of a war zone, dodging tank shots left and right while a hail of piss bullets whizzed overhead. Sarah's newer logs floated around him this time, blocking off his avenues of escape. He was left to take a powerful splash of piss water in his face as the girl dropped a girthy turd right in front of him.
The onslaught lasted for two minutes, which seemed like forever from Mark's point of view. The waterfall of pee finally trickled to a stop and after squeezing out a few more poops Sarah's asshole was done too. From head to toe he was soiled in his crush's excretions. His skin was soggy and wrinkled, tainted with the stench of her pee. He had clumps of her crap sticking to his hair and buried in his ears. Dizzy and worn out, he tread above the yellow pool avoiding the huge logs that surrounded him.
He knew what was coming next. Sarah would wipe herself and then flush him away with her shit. There was no way to survive that happening, even if he didn't end up buried in shit there was no way he could hold his breath long enough to get to wherever the pipes took him. There was only one option he had, and that was to expose himself to Sarah. Call up to her, and have her take him out of the toilet before she flushed.
A bright light assaulted his eyes. The teenage girl had spread her legs, ready to wipe off her pussy first from the leftover pee. This was the only chance he would get before being buried in toilet paper. Waving his arms in the air, he shouted as loud as he could.
"SARAH! DOWN HERE! HELP!"
The girls giant face approached as she leaned in to look where she was wiping. She had a bundled up wad of toilet paper in her hand ready to go. Mark could see her shiny beautiful eyes. He waved harder, yelling as much as he was able to before his voice gave out. Sarah's eyes turned to him, instinctively looking at the moving thing inside the toilet bowl. Their gazes met for the first time since lunch that day. Sarah stared for a second, blinked once, and then her eyes shot wide open with shock. She practically leaped off the seat, lifting her butt straight up from the sight of her own classmate inside her toilet. Was this real?
"MARK?!" she exclaimed.