"This power of yours is incredible, Ty." Mark said appreciatively, looking over his powerful human/equine body. He thought about what he wanted to happen next, and managed to get to his new hooves. He was wobbly at first, but soon settled into walking around after some experimentation. Still exhausted from his immense equine orgasm, sex was the last thing on his mind as he considered his new position more carefully. He certainly didn’t want to be a micro horse, and was becoming increasingly uncomfortable with being so small and helpless in his own living room. First, he decided, he would have Ty enlarge him.
"I appreciate you making me small, Ty, but if I’m going to remain as I am, I don’t see any point in being shrunk anymore. Don’t you agree?" Ty nodded his agreement and watched as tiny Mark walked around the carpet randomly, stretching his legs and getting used to his shifted balance. "Right," Mark pivoted to face Ty and stood with his hands on his hips and a smile on his face. "Make me big again!"
Ty got up from the couch and stood up fully. Mark took a couple steps back, gulping at his towering foster son who could easily revoke his cooperation and change Mark without consent or effort. Somehow, despite Ty’s obvious gentility with him so far, Mark couldn’t help but be frightened. He felt warm all over again and shuddered as fresh renewal of arousal washed over his body. He groaned slightly at the pleasant feeling of his testicles refilling until they were tight and big with reproductive fluid, and instinctually reached down to his crotch when his penis began to swell once more.
"T-Ty," Mark said softly, "I just wanted to be big again, not horny." Even as he spoke he could feel that two footer of his beginning to pump up with blood, while the tip was just poking out of his sheath. Ty said nothing, but Mark could sense the big young man had something naughty in mind. Mark turned away from Ty and hoped his arousal would go down, but it only increased as the pleasant warmth in his body began to intensify. A good four inches of his soft penis slithered out of his sheath and dangled towards the ground. Mark began to sweat lightly, which wetted his body down and made him smell very much like a horse. He closed his eyes slowly and moaned as more of his great member slid out of the protective sheath and brushed his thighs as he began to shake in anticipation.
He felt a large finger brush his rear, and jumped and turned to find Ty lying on the carpet facing him with a very wry smile. His penis had fully emerged from the sheath by that time, and Mark sighed helplessly and couldn’t help but marvel at it. Nearly one foot long when soft. He slowly seated himself in front of Ty and allowed his arousal to take over for the inevitable act that was to follow. He expected Ty was going to touch him, or do something else. Mark had never been keen on homosexuality, but he had to admit the thought was new and exciting. He sat back patiently and looked up at Ty’s face, which seemed to be quite joyful at the moment.
Ty reached forward and spread Mark’s legs wide. The tiny horse’s penis had begun to swell up from the unceasing warmth inside of him. Ty was responsible for that, of course. He had wanted to arouse Mark and experiment with his little equine body a little. Just for good measure, he willed the little horse to enlarge to two feet. He watched as Mark threw his head back and neighed in surprise and ecstasy while he grew bigger. When the growth quickly completed, Mark’s cock had blown up to its full erect size and throbbed with his heartbeat. Mark began to pant as a trickle of precum began to steadily flow from his tip, moistening his rod and crotch with creamy lubricant.
Mark was just about ready to burst from the intense pleasure welling up inside of him. With every second that passed he imagined he wouldn’t need any stimulation to come. His breathing was quick and urgent. "Bigger!" Mark gasped. Ty seemed happy to serve, as without a word he folded his arms across his chest and watched in complete amazement as Mark’s two-foot tall form swiftly grew larger. It didn’t feel quick to Mark at all, who savored the burning comfortable warmth that touched every inch of his body. As he finished growing at three-feet nothing, his cock was swollen as large as it could possibly go, with thick veins bulging over the intensely aroused organ, and he felt like it was going to explode. His juices flowed freely now, as Mark was just seconds away from a full orgasm. Eagerly he leaned forward, still sitting, and extended his tongue to lap at his cockhead. That did it, and as Mark licked away at his meaty penis, he was blasted in the face by steaming hot cum, which saturated his muzzle and spilled all over his shoulders, neck, and chest.
He barely had time to enjoy the first orgasm when another coursed through his system, making him stop licking suddenly to arch his torso and head back in sudden rapture. Another tremendous squirt of fluid sprayed from his tip, splattering his lower body and legs. His eyes closed and he grimaced in pleasure as yet another orgasm forced him onto his back and made him curl his legs and arms. Ty chose that point to grow Mark larger, and the horse squealed with joy as he now slowly grew up to his full six foot height. Spray after spray of thick musky horse cum jetted from his cock into the air. Ty had to back up and get back on the couch to avoid being soaked by the growing ejaculating horse morph.
At last it all subsided, and Mark was still shaking wildly for several minutes afterward. "T-Thanks Ty." Mark sad weakly, and realized he was fully grown. Perhaps even a little bigger than he originally was. He stood up, dripping with semen. "I-I think I need to go wash." Mark said, and Ty nodded from the couch. He had hesitated to pleasure Mark himself, but decided he would eventually when he got up more courage.
Mark never noticed the frozen Dustin and June as he headed up to the bathroom in a daze. Ty heard the shower turn on, willed the mess in the living room cleaned up instantly, and walked over to June and Dustin. He didn’t want to change June just yet. He’d let Mark have that privilege later, after all, she was his wife. Ty wanted to play around with Dustin!