Luke gasped and cried feeling the large Dane's member throb and pump deep within him. He felt stretched beyond imagination and was convinced that at any moment he would start to rip apart from the throbbing knot. The massive dog behind him seemed to not feel any pain as he panted contentedly on Luke's back, dribbling drops of dog slobber down his neck. As the dog calmed and lost himself in his orgasm, Luke began to notice that the feeling of pain started to ebb.
It started as just finding the sensation felt more like burning instead of possibly tearing. Soon that heat descended and spread throughout his passage and seemed to focus on his prostate gland. The heat built there, and Luke's eyes shot open as he realized that this new sensation was sensual. 'Oh god please don't let me get off on this!' He moaned to himself trying to occupy his mind with anything else. However, anytime he would focus on anything he would suddenly be brought back to his current situation as the kid's huge knot would throb and push lewdly against his prostate. As the feeling of euphoria increased he looked between his legs and begged his ever stiffening member to go down; albeit with more and more half-heartedness as the moments ticked by and his arousal increased.
Soon his mind could not cope any longer and he completely surrendered to the pleasure and the moment. His dick immediately surged to its full firmness. Then as the next throb of the kid's glorious bulb squeezed his love nut, he felt his shaft grow even harder causing the skin to feel tight and stretched almost to the point of pain. He looked back under himself and saw his member bobbing below him. It was so engorged that it was almost horizontal to his stomach, and it's normal peach hue was darker red as more and more blood rushed in. The knot throbbed again, and Luke had to throw his head back as a rush of sensual energy rushed through him, and he felt his shaft slap against his belly for a moment.
Luke breathed in gasping breaths riding the pleasure. However, his sudden movement caught the kid's attention, and he tried to pull back. Instantly sharp throbbing pain and pleasure coursed through Luke and he had to push back into the massive cock to keep from being pulled apart. Then the kid did something that Luke should have seen coming, he had seen enough dogs fuck to know that they end up standing tail to tail. However, when the kid stepped over him and began to perform the maneuver, Luke was unprepared for what assailed him. The shaft gave a sharp tug backward against the inside of Luke's hole causing him to start to let out a sharp "AH!". Then suddenly the shaft and the knot started to rotate inside of his hole from all the lubrication of the boy's cum that continued to pump into him. His initial "AH!" quickly changed note to "AHHOoo!" as the massive knot squeezed his prostate like a vice causing Luke's cock to nearly painfully begin to shoot his load all over the floor below him. His shaft remained painfully rigid pressing up into his belly as it continued to try to shoot everything out of the squeezed gland. Then suddenly the knot popped past the now drained prostate and rotated completely within him.
His eyes crossed at the sensation and he lazily leaned his head down feeling his arms trembling like they would soon have no strength left. Despite it all he felt amazing. He had just had the most mind-blowing orgasm of his life and was focusing on enjoying every sensation. The cresting waves of pleasure continued through him. The massive Great Dane now standing butt to butt with him was wagging his tail happily as his orgasm continued but seemed to be near completion. The tail swishing across his back added to his bliss and he lost all track of time. That was until he started to feel the Dane's tail starting to be hindered in its wagging as it started to hit against something at the top of his crack. It felt almost like his tail bone, but that couldn't be, he thought to himself. Soon he knew the truth as the kid's tail started slapping quickly and being stopped completely and he looked back over his shoulders seeing the 3 inch long tube of flesh sticking up above his ass. He felt a tingling rush along the new appendage as it starting to wiggle back and forth and then start to grow hair. Short, dark almost black hair, hair that was coming in very dense and completely covering the new skin, hair that was fur, dog fur.
In the space of just a few minutes he now sported the start of a tail that was covered with the same type of fur that the kid had. Suddenly feeling the gravity of the situation Luke decides to...