After school ended, Mike grew his stepdad back to his normal size, with the antidote to the shrinking potion.
Before Colin could even rant about how humiliated he was, Mike shoved a blue pill into his mouth, and washed it down with a blue potion.
Almost immediately, Colin began to feel a age regression take hold of him.
He found the loss of his age, a fact he could feel as his muscles contracted and pulsed throughout his body, rather invigorating. His penis grew erect with all the sensations and vitality flowing through him, leading him to grab at his exposed erection and begin to pump away with his hand. This distracted him from the fact now he'd already reached a college-aged young adulthood and was continuing to grow younger as his muscles pulsed and began to shrink. His hips, thighs and buttocks shrank in mass as well. Soon he could barely be considered "of college age" anymore as he looked more like a beanpole freshman or a high school student visiting campus with his tall gangly body with large hands and feet, but thin musculature. He kept pounding away, not wishing for the feelings to stop, he was feeling as though he was going to cum any moment. He hadn't had a boner this good last this long in a long time, and he didn't want it to stop.
The high school aged teen now began to shrink in different ways, namely in height. In a sudden burst, Colin nearly found himself fall over as he lost almost a foot of growth rather quickly as puberty began to truly be undone and the gangly bean pole began to lose the hair on his chest, his face, his arms, his armpits, his legs, his treasure trail, and his groin. His hands and feet also began to shrink, causing him to think his erection in his hands was growing even larger, but it was just his hands getting smaller. He soon dismissed this though as his imagination as his penis also began to feel the rejuvenating effects of youthening and began to shrink as well, growing more into the proportions of a boy at the cusp of puberty, rather than a young man completely through it.
The height of his sexual tension was palpable in his hands, he could feel it, he was about to cum, and just as the last of his former dark hair had at last faded into the blonde peach fuzz of preteens or had fallen off entirely to leave him completely bare where he'd once had hair, Colin released himself and ejected a spray of cum that fell to the floor and drained his balls of the last bit of his body clinging to maturity and adulthood. He fell back on his butt from the ectasy, eventually settling on his back on the floor. His balls became too young to replenish themsleves, shrinking and growing dormant as they began to pull higher into the sockets they rest in prepubescence. He saw his penis shrink in his messy hand, though he thought it was only a side effect from having gotten off, but in truth his penis was now shrinking to the prepubescent nub of all young boys. He however did not notice any of this as he basked too much in the sensation of having spent his load--doing so had increased the pleasure of getting younger, but had not stopped the pleasing sensations which now, in his post-ejaculation haze seemed even more intense as the feelings were no longer centered in his gut and groin but beginning to reverberate across the whole of his body. Colin let out a long sigh, which began low and shifted up an octave as his adam's apple shrank into non-existence, returning Him to the body of himself at eleven years of age, feeling rather contented and basking in the afterglow.
He almost felt grateful that his stepson was doing this, maybe he had been hard on him.
The youthening however did not stop, nor did Colin’s shrinking as he soon was leaving the double digits of his life for the single digits. Fingers and toes grew stubbier, baby fat began to appear on his tummy and his face, and the skinny boy shrank more and more in size as toddlerhood beckoned and then was achieved. His eyes seemed larger as his skull grew smaller around them, and his hair receded Into his shrinking head.
Then, he surpassed toddlerhood for infancy, and soon, he regressed right down to a one year old stark naked baby.
Baby Colin babbled in baby talk happily. Mike was impressed. “It worked.”