Ty pulled on a dressing gown and nothing else, and set out for Tom's house. Tom was one of Dustin's jock friends and had always been a total jerk to Ty for being a 'wimp', so this was the perfect opportunity for Ty to get her revenge on him.
She knocked on his door, and when he opened it she purred, "Don't ask who I am, I just have a surprise for you." As a horny teenage boy, Tom was hardly going to look a gift horse like this in the mouth, and he guided her to his room and locked the door.
"Good boy," Ty smiled, throwing off her dressing gown and suppressing a giggle as Tom's eyes glazed over looking at her feminine body. When their eyes met, Tom took her cheeks in his hands and kissed her almost forcefully. Ty felt herself moisten under his touch, especially when his crotch ground against hers. He hastily pulled off his jeans and boxers, and she removed his T-shirt- within seconds he'd laid her down on the floor and thrust his cock inside her.
Ty reveled in how eager his motions were as his hips pounded restlessly against hers, his balls slapping at her with every thrust. Not being a boy anymore was giving her a good perspective on just how horny boys were, and she found it both cute and hot. Soon she noticed his nipples had already swelled up, and pinched them, making him groan with pleasure and seem to pulse inside her. She could tell he was getting close, and decided to do one little thing to make up losing his manhood to him- she wished to ovulate again.
Inside Ty's womb, a fertile egg formed, awaiting its fertilization. Her inner walls pulsed around Tom's cock, and he hit his peak and moaned as he came hard inside Ty. His warm thick semen soaked into her pussy, and his energetic seed raced towards her egg, soon knocking her up with the second child of the day.
Once he pulled out, Tom panted loudly, and he yelped and his voice cracked as looked down at his body. "Wha-what's happening to me?" he asked. He had good reason to wonder- his figure had turned soft and curvy, he had sprouted soft C-cup breasts, and his skin was far smoother.
"You're turning into a girl," Ty explained calmly, his semen still dripping out of her. "I just spread a virus to you that transforms people's sexes, so your manhood is vanishing." She reached for the feminizing boy's tits and cupped them, making her gasp. "Don't worry, being a girl feels way better anyway," Ty assured her. "And besides, you got me pregnant with your seed, so you really don't need to be a boy anymore." She leaned into the soon-to-be-girl's ear and breathed, "You're gonna be a really good girl, Tara."
To her surprise, Tara embraced her new name very willingly. As she watched, she saw and felt her body's still masculine aspects vanish. Her penis shrank away, her balls moved up inside her and she formed a vaginal slit. In her head, it clicked- she was a girl now.
Ty kissed her, then pulled her dressing gown back on and left the house as casually as she had entered.