Mark paused as he heard a sudden wrap on the door. Mentally chiding himself, he remembered that Gene, the graduate student that lived next door, was going to come over tonight. He didn't think it was a date, more of a session so that Mary could help him with his masters thesis. There was a knock on the door again, and Mark quickly glanced around on the floor, trying to find something to cover up his nakedness. He finally settled on a bathrobe that clearly was too small for himself, but at least covered his massive tool. Sweeping his tattered clothes off to one side, he walked over and answered the door.
The tall lanky figure of Gene was what awaited him. When he had been Mary, he had thought Gene was kind of cute but a bit on the awkward side. He was a nice enough kid, certainly, just wasn't her type. Now though, Mrk saw potential in the kid, at least in one way or another. An idea started to form in Mark's head as Gene asked him who he was. "I'm Mark," he replied automatically, "Mary had to step out for a few minutes but I'm sure she'll be back in a few. You can come in and wait."
He ushered Gene inside, making sure to surreptitiously close the lid on the box of vials and carry it over into the kitchen. Gene called back from the living room, "Are you her boyfriend or something?" Mark simply laughed, "No, just her cousin from out of town. My luggage was lost, hence why I'm wearing her bathrobe. Can I get you something to drink while you wait?" Gene indicated he'd take a can of pop if she had any, and Mark knew that he had him now. He grabbed a can of soda from the refrigerator and then looked at the box of vials. Thoughts of a rather carnal nature were starting to run through Mark's head, whether it was a side effect of the newfound male sexdrive he had or simply a side effect of all the new hormones in his body, he had a sudden urge to fuck something, anything, and Gene just happened to fit the bill. But, he decided, he could change things around a bit and make Gene a bit more, palatable for his tastes. Reaching into the box he grabbed a pink vial, right next to the male one that he had used on himself. He poured it into the open can of soda, then replaced the vial back into the box. Like clockwork, the vial refilled itself, and Mark repeated the process three more times. This way, Mark figured as he smiled to himself, he'd have a woman of women to match his adonis like physique. He had to fight the urge to jack off right then and there, as his cock stood at full attention underneath his tarry bathrobe.
He walked back into the living room and saw Gene spreading out some papers to go over his thesis. He handed him the soda and watched with baited breath as Gene downed the can in a matter of moments. "Guess I was thirstier than I thought," Gene joked, clearing his throat as he did. Already Mark could see Gene's tall lanky figure slowly shrinking down a bit from the effects of the vial. "The hell," Gene exclaimed, when he looked at his hands, seeing them slowly grow smaller and his nails grow a bit longer. Gene stood up, feeling the tingling feeling all across his body. He felt his scraggly hair grow out of his scalp and into his eyes, turning a lighter brown color as it did. What little muscle tone he had softened and became smooth skin, as his shoulders shrank a bit and his waist caved inward. Mark could only watch, his hands drifting down to his cock as he unconsciously undid his bathrobe and began to stroke himself watching the transformation in front of him. Gene had shrunk a bit, falling from a healthy 6'4'' down to a foot shorter. He stepped out of his shoes unintentionally, as his pants fell down his legs, revealing smooth hairless legs where there had been hair before. He coughed again, startled by the higher lilt in his voice, as he felt his face rearrange itself to become a thing of feminine beauty. His hips expanded and his butt grew out into a large feminine heart shape, giving him the beginnings of a killer hourglass figure. Gene could only watch in horror as his chest began to balloon outwards, becoming a set of breasts the size of basketballs hanging firmly off his chest. Finally, he groaned in pleasure as his balls receded into his body, and his cock split in two, becoming a vaginal opening.
She breathed deeply and then looked over at Mark, who was now jerking off in earnest, to figure out what the hell he had done. But the moment Gene saw that erect monster in front of him, he was overcome with a sudden and unexplainable urge that aroused his new nether regions. Biting her lip, she knew she had only a few seconds to figure out what she could do. Could she run, or would she give into this new desire?