Kaizuki Hideyoshi, he had slain a dragon once - but never would he expect to keep guard of a dragon egg, and view its progress on hatching. To Kaiziuki, it was not a demotion - but rather a step up in risk. Dragons are very protective of their offspring, you see - so whether he would like it or not - someone had to take the risk for the dragonslayers of this land. Being a lithe fox (a kitsune in fact), Kaizuki has no trouble reaching his destination - being a wispy cave in the middle of a grassy plain. At least the weather was humid, and it kept his fur warm. 
Venturing inside, Kaizuki was eager to get this job over and done with. In just a few strides, he spotted the egg and nearly sighed in relief, knowing that no dragons had crossed his path yet. Yet. 
A loud, guttural roar made the fox know that he was not alone in these murky depths. Nay, for he has encountered the father dragon - all mighty, and all muscular. Not to mention, quite angry that a fox boy was treading on his sacred grounds.
The dragon was massive, towering over Kaiziuki - a large shadow forming over the kitsune’s entire body from its sheer muscular size. It huffed out a puff of heated air through its nostrils and looked down on him with deep, black eyes, lit with a fire of rage. 
Kaizuki whimpered under the huge hulking form of the dragon, who looked like he could stomp him under his foot. Mumbling apologies, and fumbling back to the cave entrance - Kaizuki's best interest right now was to get the hell away from that egg and the massive, angry father dragon. 
The dragon's gaze shot down to Kaizuki's exposed rump - and the dragon licked his lips hungrily, and his cock started to slip out of his sheath in all its full erect glory.
To the sight of the fox fumbling at the floor - scrambling to get away - riled the pent up dragon's senses up, making him erect to full hardness in no time. 
The grey-scaled dragon stomped over to Kaizuki, covering the entrance with his face. As Kaizuki panicked and turned around to retreat further in the cave - he was met with the dragon's huge knotted cock instead. 
Judging from the short, hot and lustful breaths of the dragon above him - it was quite clear that the dragon had trapped him in here to mate with him. 
“Whoa whoa, hang on. I'm a not a female, you can't just--Nnngh!” It was clear Kaizuki was not going to have a say in the matter, as the dragon had manhandled him to the point where that flared spiky tip was pressing against his bottom, making the kitsune tense up and bare the inevitable. The dragon huffed and puffed as he was entering his throbbing pride inside his newly found fleshlight. 
“G-Guess its mating season for the dragons then, huh…”
Kaizuki could feel that huge, thick and throbbing dragon cock fill up and stretch his ass to an immeasurable length - the spiky tip kept hitting his prostate and sending waves of pleasure throughout his whole body, the tip and spikes of that cock were making his fur stand on edge and body tremble with anticipation. There was no greater feeling than this, even if Kaziuki was not prepared, his ass clenched around the thick precum covered manhood of the dragon in a vice grip. 

The dragon grunted out deeply, huffing out puffs of heated air through his nostrils, as he continued assaulting his sex victim - now used as nothing but a fleshlight for his own desires. His large grey-scaled balls whacked the kitsune’s plump ass with every thrust, lurching the kitsune’s body forward from the kinetic energy. His fat knot kept bumping into his furry ass too, making Kaizuki feel anxious about what was to come next. Squelching sounds filled the room - accompanied with deep grunts and high pitched whimpers of submission. Even still, the dragon gripped the body in his entire paw - akin to a predator hunting his prey. Except, in this instance, the predator was unbelievably horny from months of abstinence and the prey had a plump ass. What animal could pass up a great fuck like this? 

Everytime the horny dragon thrusted into the tight ass of his victim, his muscles filled with new life from the fervent breeding - throbbing forth, becoming larger with the veins under his grey scales starting to pop out. Eventually his chest grew so massive and powerful, that it pressed against his kitsune victim; the warm heat from the dragon's muscular chest and his powerful breaths were the most dominant things Kaizuki could feel apart from that huge cock that was lodged inside him - growing bigger and bigger as the dragon's muscles grew with it, expelling forth ropes of pent up precum from its spiky tip in the process. 

Kaizuki audibly shuddered. His paws and legs dangled in mid air as he was being held up from the sheer strength of the dragon's cock. His body trembled and his breath was shaky as the daddy dragon was pile driving his fat cock in him like it was the best hole he gets to fuck in his life. But to a sex crazed and virile animal like that, what would it matter? Every hole is a goal. 

Then, after all the incessant fucking and throbbing, the kitsune felt the cock bloom up in him; the spikes hardened but they were not hurting him. It was a way to keep the dragon's personal little fuckmeat in place, even so - Kaizuki had long abandoned hope of getting off the gargantuan cock anyway. He felt the knot thrum and engorge then, with a final thrust in his backside, the dragon had impaled his little fleshlight fully on his daddy cock. 
Now that the whole thing was in his body, knot and all, Kaizuki looked down to see his stomach bulging with that fat buried inside his body. 

The dragon definitely seemed glad that it had found a little fucktoy to dump its cum into, as it grunted out deeply and heavily - filling his kitsune victim to the brim with icky feral cum. Just from the sheer amount of it, it bloated Kaziuki’s belly and inflated him like a balloon - to the point where where cum came pouring out of his nostrils and mouth. 
After minutes of what seemed like an endless orgasm, the flow of cum stopped - but Kaziuki was absolutely bloated with it as a result. He felt the huge cock that was jabbing him, starting to soften - and retract back to its huge sheath. The knot was still swollen and engorged, and the dragon definitely took his time untying from his sexy little fleshlight. 
But, once he did, cum came pouring out of Kaizuki's gaping ass - now that the floodgates were open. 
He fell unconscious, from exhaustion and fatigue. Kaizuki wasn't sure what was going to happen next, but the dragon definitely was. He was going to continue being his little fucktoy all throughout the mating season!