Post a scat image, then write a little story about it! (I debated whether to put this in /lit/, but since it's scat based and has images, it goes here.)
The teenage girl walked hurriedly towards the bathroom, derriere obviously clenched in fecal desperation. As she came in view of the door, I saw her freeze and a look of panic cross her face; she had obviously let a spurt of feces escape into her panties. However, she regained control and went into the bathroom. I followed.
In her urgent desperation, she had not even stopped to lock the stall door. I opened it just as she lifted her skirt, about to pull down her white panties. Well, they had been white once, but now they were soiled, stained brown by liquid shit. As I flipped her around, bending her over the yellow-faded plastic toilet toilet seat, I wondered what was the cause of her digestive disturbance. Dodgy food? Another virus going around the high school? Some allergy or chronic malady? Or maybe she was one of those girls who abuse laxatives, thinking it will make them thin and pretty. If she was, that was foolish of her–anal purging causes more vitamin deficiencies than weight loss, and often swells the stomach–but she would richly deserve what I was about to do to her.
"I have a knife," I whispered in her ear. "Don't scream." Pulling aside her stained panties, I thrust my erection into her leaking anus, already lubricated by her liquid shit.
She did not scream, but she couldn't help but moan as my cock slid into her shithole. Her anus had already relaxed in preparation to release its long-held diarrhea, but she was still tight around me as I began to thrust into her inflamed rectum. Her bowels felt impossibly slick; retaining her acid slurry for so long had caused them to produce great globs of rich anal mucus, far surpassing any sour wetness a pussy can produce.
I drove my penis into that slick, stinking tunnel. With every thrust, I felt her shit splash in waves against the head of my dick. Every time I pulled out, my length was smeared, and each return deposited that smear on her raped asshole. The girl gripped the edge of the toilet seat, staring back at me as she cried softly.
I could only imagine the pain she must have been in. Goodness knows how long she must have been holding in that urgent shit–perhaps an entire class period–and then, just when she expects release, a stranger anally rapes her and plugs the sickness' peristaltic exit from her body. Indeed, that body shuddered around me, not with pleasure or sobs, but with what must have been excruciating cramps. The pressure against my glans would increase, and a small spurt of brown effluvia would escape from her stretched ring and drip down my balls. No matter her body's efforts, though, my cock plugged the escape of her pain. Instead, it had to rumble and gurgle through her squittering bowel, backwashing it with darmic agony.
"Shit on my dick," I told her. "Push like you're trying to shit it out. Make it good for me, and this will be over sooner."
She nodded at me, red-eyed and teary. I felt her girlish ass bear down, and the increased force of her diarrhea against my dick became ecstasy. Some of it sprayed out around my cock, coating my pubic hair with vile ass-jism. The deliberate effort seemed to give the girl some intestinal relief, and I regretted the reduction of her agony (a girl writhing with colic is the most arousing thing on earth, save for that girl also shitting), but the increased stimulation more than made up for it. The pleasure of the act sang along my nerves, creeping up my shaft towards the shit-plowing head of my penis. The ecstasy crested at the rim of my pisshole, and I ejaculated, adding my semen to the raging liquid distending the girl's colon.
But I wasn't done yet. There was a reason I'd even seen the girl as she walked to the restroom. Softening, but still half-hard, I relaxed my cock's sphincter and pissed, hard and voluminously, into the girl's anus.
She began to scream, feeling the sudden stretching influx, but immediately muffled it with one hand, remembering my warning. I continued to piss, filling her up to bursting, my hot yellow salt mingling with her diseased brown. At last, emptied, I withdrew, and her panties snapped back over her cockblasted ring, trapping her now-cold first spurt of filth against it.
Of course, there was no way she could have held her bowels now, even for a second. Mingled diarrhea and piss fountained out of her asshole, drenching her already-ruined panties and running down her legs, soaking her cute kneesocks and school shoes before it puddled on the tiled floor. For a few minutes I watched her sobbing over the toilet bowl, defeatedly expelling waves of what was now pure liquid shit into her panties, but I was too spent to get it up again. Eventually, I retreated into another stall to clean myself up. However, before I left, I made sure to take some pictures of her soiled, ravaged ass. It's not often I get a fuck like this!