With his eyes locked on his image in the mirror, the tingling intensified. It was actually a very pleasurable feeling - Mark's dick started involuntarily reacting, causing the cotton panties to strain.
The first change was his height. He immediately lost about 3 inches, making everything in his room seem just a little taller. Next, his feet shrank to a more petite size (and the shiny black shoes seemed to reform to accommodate). He couldn't see it yet, but his now perfectly-manicured toenails were now painted a very girlish pink.
The change moved up his legs, removing the peach fuzz he'd just started growing recently. His thighs thinned a bit and his butt grew just enough to push the rear of his pleated skirt out a little.
His tummy flattened and two small bumps pushed into the training bra. His newly sensitive nipples felt amazing against the material of the bra. Moving up his torso, the change made his neck and arms more slender (and just as hairless as his legs), and his hands were now smaller and more feminine (with a nail polish shade to match his toes).
Next, his hair began to lengthen and lighten from the dark brown color he'd always known to a dirty blond. As the hair grew it tied itself into pigtails. His eyebrows thinned and became a matching shade of blond. Boring brown eyes recolored to a bright blue and lips puffed slightly. His nose thinned and upturned a bit, followed by his chin pointing out a little more to achieve an aristocratic look.
Finally, an intense feeling of pleasure let him know that his dick and balls were being pulled into his body and reformed into a new vagina.
As the tingling subsided, Mark was still breathing heavily when he made eye contact with the new girl in the mirror. She seemed to be the same age as he was, and looked every bit like a stuck-up St. Mary's student. Except it seemed he was now that student.