The rottweiler waits with an anxious patience, standing on the alley floor worn grey by weathered time and countless use.  The shackles' steel, slightly warmed by his body heat, pushes against the spreader bar, reminding him of his inability at self-protection.  He resigns himself to wait as patiently and calmly as he can so that his mind doesn't conjure anything up worse than what will happen, and so that he's as relaxed as possible for the inevitable.  As he hears the top's heavy footsteps fall loudly in the echo of the silent space, and the crunch as they strike the occasional patch of gravel, he awaits his anal deflowering as the bottom virgin he is...

The anthropomorphic rottweiler approaches, laying eyes on the dog for the first time--all secured and ready.  One look at his exposed assets turns him on immediately, and he walks closer.  He can feel his nub wag with happy anticipation through the hole in the seat of his pants.  The erection in his jeans is straining to get out of its sheath.  He's more then ready for this, but he wants to be a gentleman about the whole thing. This is his first time using a back door, and he assumes as much for the dog as well.  He wants them both to enjoy it, and he always intended to go gentle. 

He walks up to the dog's rear at a medium pace, not too slow as to prolong the inevitable, but not too fast as to scare the dog.  As he reaches his quarry, the biped canine walks in front of the bound rottweiler and kneels down to meet his gaze. As he stares down that blunted muzzle, he sees fear and apprehension in those big, brown eyes.  He gently strokes that big, solid cinder block of a head.  "It's alright boy, I'll go slow and easy.  I want this to be mutually enjoyable for the both of us.  I bet this is your first time, too?" 

He pats the dog's solid head before walking behind him. As he walks to his lover's business end, he starts to undress and reveals his sheath, his thick, tapered penis and sizable knot bulging through the furry skin.  As he walks, he runs his right hand along the dog's head, neck, and back. He feels a twinge in his shaft as his thoughts wonder to that tight exit and how it'll feel.  When he reaches his destination, he pats the rottweiler's muscular rump.  Standing behind that spread rear, he's excited to get down to the business at hand at the business end.

He squats down and rests the worn knees of his Levi's on the hard concrete, staring at the glory hole for a moment.  He places his hands on the dog's muscular hamstrings and proceeds to gently kneed the flesh and developed muscle beneath it, working his way to that wanted hole beneath a bobbed, erect tail that seems to act as a destination marker or a flag on a golf course, highlighting his prize.  He can sense the dog relaxing and the tension releasing from his body as this unofficial masseuse plies his trade. 

Continuing the foreplay, he inserts his index and middle fingers--already trimmed of their nails--into his muzzle and sucks them for a second.  Slowly removing them from his muzzle, he aims them at his target and gently inserts one, then both in an effort to loosen up his virgin, moving them around in his lover's tight, forbidden passage.  Like an exam at the vet's, he goes in deep and probes his lover's prostate, rubbing both lobes of the walnut-sized sex organ.  As the dog tightens involuntarily, his lover croons to him to stay calm and reassures him that this is for his benefit. 

After removing his probing digits, he places his muzzle on the dog's anus and gives a gentle peck, then begins to kiss and lick the tight, pink hole, feeling the tension of its muscle melt away. With his subject thoroughly relaxed and calm, the anthro canine opens his muzzle and gently licks the dog's firm, tightly-held balls, maneuvering the hefty orbs inside their black nutsack with his tongue.  The cool, wet surprise elicits a shiver from the dog, but he's pacified by a whispered "Just relax, it's ok." 

The anthro rottie slightly inclines his stubby muzzle and gently licks the dog's hole once more, sensually rimming and reaming him out.  The dog begins to pant and whinge at the sensation, then thrusts his rear against the air as best he can to feel that strong tongue toying with his virgin hole, providing needed lube and a natural muscle relaxant.  The anthro continues eating out his lover's ass, the dog thrusting against the probing tongue as lewd wet sounds fill the air.  As the dog is calmed completely, he's ready to be "taken." 

With the foreplay over, the anthropomorphic rottweiler gently yet firmly grasps the male's developed hips and slowly offers the tapered tip of his sheathed penis to the dog's slightly loosened and copiously lubricated virgin anus.  As he slides in, he instantly feels the warmth and constriction of the sphincter and anal walls as he slowly descends.  Once inside, he starts to gently thrust like the piston of an old steam locomotive.  He's slow, with long, full strokes, increasing the rhythm and speed.  As he thrusts, his knot continues to grow in size, pulse by pulse, until the two are tightly tied together, the top's knot stretching the bottom's rectum to its limit.  The dog's tight anus clamps down behind the anthro's knot, and he begins to ejaculate, shot after shot of semen plastering the four-legged's insides. Time seems to drag on or stand still entirely as both beings wait for nature and evolution to take its course... with nothing but time on their paws and hands, the anthro pats his lover on the side and tells him he's amazing.  Continuing to praise the dog, calling him a good boy and an amazing lover, he reaches around and fondles the bottom's nuts.  He can feel his phallus throb and pulse as his lover's own heartbeat pulses against his meaty organ.  Thanks in no small part to canine knot firmly pressed against canine prostate, the dog begins to release, both of them unloading a torrent of lust and pent-up want as the rottie's heavy nuts contract over and over again in his hand.  With his other hand, he gropes his lover's sheath behind the knot, feeling his bottom clamp down tightly with each squeeze as he squirts loads of doggie cum on the ground.

With his four-legged lover's bowels sufficiently drowned in his potent genetic legacy, the two-legged lover reaffirms his grip on the other's thighs and starts to pull out.  As he reverses his pelvis, the feral dog's anal ring pulls back as the knot is dragged out, the dog feeling his ring follow the contours of his lover's tie.  Once it's almost halfway out, the anthro top stops and waits for a minute, the bottom's anal sphincter stretched beyond capacity by the baseball-sized knot.  The dog squirms as the anthro consoles him.  “I know, boy... but we need to stretch you a bit.”  Then he sinks back in, letting the dog's hole relax for a moment longer.

After a short time, he bends over the dog and whispers in his right ear, "Ready, sweetie?  One... two... three!”

With that final number, he rips his knot from the other's ass to a startled yelp. But as dogs will do, the bottom quickly forgets the momentary pain and his nub starts wagging instantly. Once both lovers are free, the anthro bends down and licks the evidence of their love away, causing sexual electricity to serge through the other's body as his loose, worn-out hole is soothed by the caress of the top's tongue. 

With the tradesman's entrance seen to, it's back to the front door. The biped strides back to the dog's head, and kneels down and lowers a worn knee from his Levi's onto the concrete. He rubs the dog's head and animatedly praises him for being so good, in doing so making him forget about his posterior pains. He then rises in front of the dog's face, his used penis at a shallow angle letting his quadruped counterpart get the full view of his solid and bright red shotgun-like shaft and baseball-sized knot, dwarfed only by his huge nuts.  Bending at the waist, he slightly bends his knees and carefully, deliberately stretches his torso over the dog's back, bending his elbows and supporting his weight with his hands on either side of the dog's spine as he descends. Once positioned, his 12 gauge phallus is directly at the dog's muzzle, which the dog instinctively starts to lick both out of curiosity and the recognizable scent of strong, virile male musk, as well as whatever residual semen is left from their anal liaison.  He licks and licks, enjoying himself and making his lover quiver at the sensation on his impossibly hard penis. As he starts to thrust his muscular ass and hamstrings, humping the dog's muzzle, the dog starts maneuvering his tongue, swallowing the top's semen as quickly as it's dolled out to him, the ejaculations occurring with renewed force.

The anthro rottie pants and thrusts hard, getting as much fun as he's sure he's giving. As his erection finally begins to subside, he withdraws from his muzzle-humping position and kneels by the bottom's side, gently massaging the dog's muscles from head to toe as a way of saying thanks.  Eventually, he puts his now completely flaccid penis back into his underwear and jeans and does himself back up, kneeling down to look the dog in the eyes again.  “Great work boy, you were amazing.  I hope you enjoyed this as much as I did.”

With that, he removes a key from his shirt pocket and stands back up. Walking to the dog's rear for the last time and crouching at the shackles, he gives the dog one last parting fondle of his heavy sheath and balls before unlocking his bonds and walking out of the alley.