Any reply Derrick might have had was lost as his enlarged penis demonstrated a much greater sensitivity - sliding his new foreskin down sent a powerful sensation of pleasure that made him shiver. He gasped and arched back in the pool as Hebe continued to masturbate him, his slender body trembling as he pounded erect.
Hebe grinned at the foolish boy - he was already larger than almost any grown man, which would cause him a lot of problems. Clothing would be difficult at best, and he would find that the vastly improved equipment would react to almost any stimulus. He could easily become aroused by almost anyone or anything he found attractive - girls, boys, animals. However, no human would risk such a huge tool penetrating them, and only larger animals would be able to accept him. How bog COULD she make him, though? The question had never come up before, and she was curious to find out. Being centuries old, there were few things left to challenge her abilities.
Derrick was too lost in the growing orgasmic haze to complain, and he had asked just how big she could make him.
She started using both hands to pleasure the boy, fingers slipping under and around the growing orbs of his testicles. They stretched the flesh of his scrotum as they swelled out under a shaft that thickened and lengthened with each handful of water from the pool. Veins swelled, and the cap flattened some as she guided the growth towards a more equine shape. Derrick now had a 15-inch shaft standing up rigidly between his legs, which were beginning to shift apart to accommodate the spreading girth of his cock's base. He was getting taller - she could see his legs had stretched out. Sixteen inches, seventeen. A stallion would be proud to have such a tool, and still it grew.
Derrick was confused by the powerful sensations, hands groping blindly for the source of his pleasure. His fingers brushed what felt like one of his legs, only to be batted aside by Hebe. Pressure continued to build and he grunted and moaned with need to release.
When her efforts finally stopped causing an increase in size, Hebe helped the struggling boy reach climax. He cried out as he arched back, his entire body going under water except for the rigid flagpole of his cock The eruption of semen was impressive even given the size of his testicles, and he shuddered twice more in release before going limp. Hebe lifted his head up above the surface as he spluttered and gasped, still trembling from the intense physical and mental experience. Blinking, Derrick looked up at her with a weak grin. "That... was... scary... amazing." It wasn't until he started to struggle to a sitting position that he discovered the true results of Hebe's handiwork.
The penis still standing erect between long, skinny legs was impossibly long and thick , a heavy dark brown foreskin sagging down around the slick, pinker shaft and flattened end. He was actually looking up at the cap, which looked to him like that of a horse. The throbbing organ was longer than his arms, easily 25 inches and probably longer. He forced himself to look down and saw the base was at least six inches in diameter, and the still-taught sack underneath held clearly-defined testicles that were bigger than softballs. Hebe grinned at him. "You asked what my limit was. This appears to be it."
Derricks eyes widened in horror and he scrambled up awkwardly, nearly falling as an unfamiliar body struggled to coordinate. Hebe helped steady him as he managed to stand shakily. He was much taller than the woman now, his body slender and still hairless, and when he turned to look in the mirror, still a young teenager. But he was close to seven feet tall now, with skinny arms and legs stretched out by some fantastic growth spurt, ending in large hands and feet. His face had lengthened and features were coarser, even though he was still recognizable. However, all that was secondary to what had happened below his waist.
He literally looked like he had three legs - the enormous cock was now hanging limp, but the end swung well below his knees. And his hips were spread so that the gap between his thighs allowed the massive testicles to hang loosely. As he stared, liquid dripped from the end of his cock and splattered on the marble floor. Another drip followed, the off-white fluid easily recognizable as semen.
Hebe clucked her tongue. "It seems you are going to be rather messy to have around. If you are already dripping right after three ejaculations, I expect you will have a constant stream most of the time."
Derrick finally found his voice. "I'm a freak!" Despite the massive changes elsewhere, he still sounded like a 13 year-old boy.
"Yes, quite the oddball." Hebe chuckled, enjoying the boy's shock and horror. ""I'm afraid not even the largest draft horse could take you inside, though it was obvious you get plenty of pleasure just from masturbation. And I expect there is no point in trying to wear any kind of clothing."
Still transfixed by his own reflection, Derrick reached down and hefted the thick shaft with both hands. It was heavy, and the thick tube of his foreskin hung loosely off the end like a too-long coat sleeve. He pulled back the covering to look at his horse-like tip, only to shiver as it caused powerful sensations of pleasure. That shiver became a shuddering gasp as a jet of semen shot from the end. Derrick staggered, panting as he let the immense organ drop. It slapped against his legs, causing more semen to splatter out. The incredible pleasure had rocked him to his core, yet he could not imagine trying to live like this. "What am I gonna do? I can't go out like this!"
"On the contrary. young man. This is one place where you can go anywhere you want!" Hebe grinned. "And for the next two weeks, this is what you will live with. Unless you want to get aged up - remember that this is you at 13. Just think what you would look like restored to 17, or even better, matured to 20!"
Derrick stared in the mirror. It was true - he had become a young kid. If this was just the start, what would he be like in a few years? Despite lingering horror, he tried to picture a 17 year-old version. He was already a freak that could not go out in public. If maturing brought the same changes it had before, his cock would drag the ground by the time he reached high school! Tears started to frm in his eyes and ran down his cheeks. "Please! I didn't want this! I.. I'll do anything!"
Hebe's expression softened, and she reached up to stroke his cheek. "Do not despair, young one. This is only for the time you are here. When the time comes for you to leave this place, I promise that you will be normal again. Perhaps somewhat enhanced, as a reward."
"What about my family? They'll freak out!"
Nodding in agreement, Hebe began guiding him towards the exit. He shuffled automatically, the wide hips and heavy cock causing him to lurch slightly. "Everyone will stare, many will come to examine and touch. Being a freak here also makes you an attraction. After a few days you'll be so used to having people treat you as a fascinating beast that you won't even think it unusual." They had reached the exit t the main Spa, and Hebe patted his butt. "Go on, now. Time to show off!"
Derrick shuffled automatically at the prompt, pushing through the curtain and into the waiting area. There were several other customers, all of whom gaped when they saw him. Even the receptionist stared, but then grinned and gave him a 'thumbs-up.' Derrick's cheeks were hot and he wanted to cover himself, but even the large hands that were now his were laughably inadequate. Sighing, he made his way out into the huge reception area where he and his family had first entered. The audible gasps and shocked stares made him cringe, but there was no place to hide. The presence of the massive, naked minotaurs and centaurs helped some, and he gradually realized that no one looked horrified, just amazed. Many of the guests were now grinning at him, and the staff seemed to have accepted his appearance as normal. Looking down, he saw a small pool between his feet just as another large drop of semen hit it. What was he supposed to do now?