Illustration and Comic by Yetigo
"Bocci,” Professor Tok motioned toward the back of the class, “please approach and mount the subject."
A hulking, shaggy form detached itself from the crowd, padding forward on digitigrade paws that clicked against the smooth floor. As it emerged into the light, Juro beheld a creature straight out of myth - a humanoid form with the unmistakable features of a canine. Pointed ears swivelled atop a large head with a protruding muzzle. Bocci stood upright like a man, but was covered in a dense pelt of mottled grey and white fur.
The doglike alien loomed over Juro's splayed form, its great barrel chest heaving with eager pants. A long, pink tongue lolled from its jaws, dripping strands of saliva onto Juro's trembling skin.
"Remember to prepare the subject before penetration," Professor Tok instructed. "Olfactory stimulation and external lubrication will ease the passage."
Bocci gave a rumbling growl of acknowledgement. The beast lowered its shaggy head, pressing its damp snout between Juro's spread cheeks. It inhaled deeply, huffing and snuffling at Juro's most intimate area. Juro squealed and writhed in mortified protest, but his restraints held him fast, leaving him no escape from the alien's shameful inspection.
Seemingly pleased by Juro's scent, Bocci began to lap at his twitching hole, the broad tongue slathering the puckered flesh with wet swipes. Juro gasped at the foreign sensation, electric jolts of unwanted pleasure zipping up his spine as the slick muscle probed and wriggled past his rim.
"Ah yes, excellent technique," Professor Tok praised. "The Fido race's saliva glands produce a viscous lubricant with arousing and relaxing properties. Thorough oral preparation will make the breeding process easier."
Bocci growled its understanding, the rumbling vibrations traveling straight to Juro's core. The beast continued its sloppy ministrations, tongueing Juro open with obscene slurps and satisfied huffs. Juro could only moan and shudder, his body growing lax and pliant despite himself under the relentless stimulation.
Eventually, Bocci pulled back, its chops glistening with slick fluids. The alien beast rose to its full imposing height, caging Juro's splayed body beneath it. Something hot and heavy slapped against Juro's belly.
Juro lifted his head to look down and immediately wished he hadn't. Jutting out proudly from Bocci’s furred haunches was a straining red cock. Nearly as long as Juro's forearm and as thick as his wrist, the tapered tip drooled clear precum.
Bocci fisted his shaft, giving it a few rough pumps as he lined himself up with Juro's entrance. The head prodded at the opening, painting it with musky fluid.
"P-please," Juro stammered, trying to wriggle his ass away from the weapon aimed at it. "It won't fit!"
Bocci just laughed, a harsh, barking sound. He gripped Juro's hips in his clawed hands, claws pricking against vulnerable skin as he yanked the human flush against his groin.
Juro screamed, head thrashing against the table as he was impaled like a pig on a spit, opened wide by creature’s cock. Despite all the stretching and preparation, it still felt like he was being torn in half, his tender opening penetrated and forced wide around the alien’s prick.
Bocci groaned in satisfaction and started to piston in a ruthless rhythm. Each thrust slammed against Juro's prostate, battering that tender bundle of nerves. Pleasure and pain surged through his ravaged body in sickening waves.
Bocci rutted into Juro with animalistic abandon, his heavy balls slapping against the human's upturned ass with each brutal thrust. Juro could only lie there and take it, his body rocking back and forth from the force of the alien beast's thrusts. Drool flew from Bocci's lolling tongue, splattering Juro's face and chest as the beast grunted and growled above him.
Professor Tok observed the breeding dispassionately. "Notice how Bocci's penis has a tapered tip to facilitate penetration, but then widens at the base. This is a common feature in canid species. The swell of tissue is called a knot and serves to lock the mating pair together to ensure successful insemination."
As if on cue, Juro felt a painful stretching deep inside his abused channel. It felt like a fist expanding in his guts, pressing mercilessly against his tender walls. He wailed in agony as his rim was forced impossibly wider around the growing bulge at the root of Bocci's cock.
"Ahh yes, he's starting to knot," Professor Tok narrated with clinical fascination. "The knot can swell up to twice the width of the penis itself. This ties the male inside the reproductive channel, preventing him from withdrawing until his seed has been fully expelled. It also provides constant stimulation to the mate’s internal erogenous zones."
Juro sobbed brokenly as the knot reached its full size, locking him in an unbreakable fleshy tie with the rutting beast. His hole clenched and spasmed weakly around the massive intrusion, walls fluttering in helpless submission. He felt impossibly full, stuffed to the point of bursting. The unyielding pressure against his prostate sent revolting sparks of pleasure arcing up his spine.
Professor Tok continued his lecture as if Juro wasn't being split apart before his very eyes. "Each of you comes from a species with unique reproductive anatomy and techniques. This diversity ensures genetic compatibility with a wide range of hosts. Over the course of the breeding program, the subject will be exposed to and seeded by all of your varying traits to maximize the chances of successful fertilization."
Chirps and clicks of anticipation echoed through the room.
Bocci gave a guttural roar, hips slamming flush against Juro's ass as he ground his knot in as deep as it would go. Juro felt the beast's cock pulse and swell even further inside him, the shaft flexing against his battered walls. Then scalding heat bloomed in his core as Bocci began to come.
Juro wailed as he felt the first gush of semen flood his insides, painting his tender walls. Bocci's cock continued to flex and spurt, pumping what felt like gallons of thick, virile spunk into his body.
The sheer volume of ejaculate was inhuman, an endless torrent that filled Juro to overflowing. His belly felt tight, bulging from the sheer amount of alien-dog come being pumped into him. It sloshed and churned in his guts with each flex of Bocci's cock, the pressure building until Juro was certain he would burst.
Perversely, his own cock began to twitch and jerk against the confines of its cage, a sympathetic orgasm triggered by the constant assault on his prostate despite the denial of any external stimulation. His balls throbbed and ached, but he was unable to release. Juro sobbed at the cruel tease, the ruined climax only adding to his torment.
Bocci's output finally began to taper off until he was just grinding against Juro's ass, each rock of the alien’s hips jostled Juro’s belly full of come, yet the knot kept him stuffed full and plugged up.
"Exceptional virility," Professor Tok remarked, eyeing the prominent swell of Juro's come-bloated belly. "A promising start to the breeding program. Bocci's potent ejaculate has thoroughly seeded the subject's womb. With any luck, fertilization will occur and embryos will begin to develop over the next few cycles."
Bocci made no move to withdraw, his softening cock still buried to the hilt, plugging Juro's hole and keeping all that dog spunk trapped inside him. The knot showed no signs of deflating any time soon, an unyielding stretch that made certain not a single drop of come would escape.
Professor Tok nodded in satisfaction at the thoroughly bred human. "Bocci will remain tied for some time to allow for maximum sperm retention and increase the chances of successful impregnation. This process can take up to 30 minutes in canid species."
Juro whimpered at that pronouncement, the idea of being tied to the beast for that long filling him with revulsion.
The alien professor turned to address the class. "In the meantime, we should continue stimulating the subject to encourage his body's adaptation to its new role," Professor Tok advised. He gestured with a tentacle to Juro's chest. "Focus on the oral region and mammary glands - these erogenous zones are key to reinforcing the feminization process."
Bocci rumbled his understanding. The beast leaned down over Juro's trembling form, his great shaggy head hovering inches from the human's tear-streaked face. Juro cringed back into the table, trying to turn away, but Bocci grabbed his chin, forcing the human to meet his hungry gaze. Juro struggled but was held fast by the restraints and the thick fleshy tie still knotting him to the alien dog.
Bocci's long, pink tongue unfurled from his muzzle, licking a wet stripe up Juro's cheek. Juro shuddered in revulsion, squeezing his eyes shut as the beast began to lap at his face, covering him in drool.
"Good, oral stimulation will help increase oxytocin production, strengthening the male's instinct to bond with his mate and offspring," Professor Tok narrated approvingly.
Bocci growled in acknowledgment and crashed his mouth against Juro's in a mockery of a kiss, pushing his lips apart to plunge that thick, slick tongue inside. Juro gagged at the intrusion, the musky taste of his own slick coating Bocci's lolling tongue as it mapped out his mouth. Drool dribbled down his chin as Bocci licked into him possessively, claiming him inside and out.
Bocci's clawed fingers found Juro's swollen, throbbing nipples, still red and puffy from the milking pumps. He scraped the sensitive nubs, sending jolts of pained pleasure straight to Juro's core. Juro whined into the plundering kiss, back arching as much as his bonds allowed, shamefully presenting his chest for more of the sweet torment.
Juro shook his head, whimpering as the alien dog relentlessly worked over his engorged nipples. Each cruel flick and scratch seemed to send a bolt of sensation straight to his stuffed hole, making him clench reflexively around the glans still splitting him open. His own member twitched weakly in its cage, a few pathetic dribbles of clear fluid smeared across the metal.
Professor Tok hummed, taking note of Juro's reaction. "Excellent, the subject is displaying a strong connection between nipple stimulation and internal pleasure, a key marker of induced lactation. With regular milking and hormone treatments, he should begin producing milk suitable for nursing your hybrid offspring."
Bocci growled in acknowledgment, rolling and tweaking Juro's nipples between deft claws. He dipped his head to lap at the tender peaks with his tongue, drawing the swollen flesh into his mouth to suckle greedily. Juro mewled at the sensation, toes curling as the keen pleasure-pain shot straight to his aching groin.
As Bocci mouthed and milked Juro's sensitive chest, his knot finally began to soften and deflate inside the human's stretched hole. With a wet squelch, the beast's spent cock slipped free in a gush of semen that pooled under Juro’s ass.
Professor Tok nodded in satisfaction. "Excellent work, Bocci. You may step back now."
Bocci gave Juro's chest one last possessive lick before pulling back. The alien beast's cock hung heavy between his haunches, still dripping strands of musky ejaculate. Bocci’s tail wagged lazily as he padded back to join the other students.
Juro shuddered in relief and disgust while his abused rim clenched weakly, trying in vain to close after being stretched so wide.
Professor Tok peered between Juro's obscenely splayed legs, clinically examining his freshly bred hole. "Very good. The subject's passage shows optimal seeding - gaping nicely, and deposited thoroughly with your genetic material. His birthing tract has been firmly plugged and filled to capacity."
Professor Tok turned to the waiting class, tentacles undulating in excitement. "Who would like to breed the subject next?