After Jeff pressed "Start" he took his shirt off, leaving just his black boxers, the way he normally slept. He crept to Kara's room and laid down in her bed. It was tough to fit his tall, male body into the small bed, but that wouldn't be a problem for long. He soon fell asleep, dreaming of how his sister's body would feel to live in tomorrow.
Jeff woke in a strange haze. His mouth and face felt strange. There wasn't the normal smell of a sweaty teenage boy waking up, but the calm, nice scent of a young girl. The sun was shining through the windows as his eyes adjusted to the light.
Realizing what had happened, he pulled the sheets back. He couldn't believe what he saw. Below his head were two short, skinny legs wearing soft, grey pajamas. He held a hand up and saw a little girl's hand. He touched it to his face and felt something completely new.
The boney, ugly boy face Jeff had become accustomed to was replaced with the entirely soft, beautiful face of an 11-year-old girl. It worked! Jeff was a young, beautiful female, just as she had always imagined.
Jeff nervously rubbed her hands down her neck, down her torso, and around her pajama bottoms. Her dick and balls were gone. She really was a girl. She cautiously pulled her pajama bottoms and her panties outward and saw her hanging, awkward genitals replaced with a beautiful, simple vertical slit.
Jeff felt incredibly awkward seeing Kara's vulva, for the first time since they had been kids. Jeff remembered marvelling at the baby sister, born with a slit and no penis, learning that is how girls are born and how they have to grow up. For the first time, Jeff got to feel that bizarre empty sensation. She touched her finger to the little mound between her legs, and gently moved it down to feel the strange vertical slit. She had two thick lips of flesh on either side of it. It was the first vulva she had ever touched.
Jeff pictured how different her body was. She had always had a bladder to store pee, which connected to her weiner to let the pee out at any time and in any direction she wanted, standing or sitting. She had always had intestines to store poop, which she had to release out of her butt. Now, she had something new, a uterus, tucked neatly behind her bladder, which connected to her ovaries to take care of her eggs. She no longer needed to carry around testicles in her scrotum, since she had no need to create sperm. She no longer needed a penis to impregnate women with her sperm, since she would be the one impregnated. So her crotch was completely flat and she didn't need any external genitals at all. Her bladder would simply squirt pee out of her vulva with no ability for her to guide it with a penis. Instead, she would have to let her vulva direct the pee any way it wanted, and she would have to clean up the mess left behind with toilet paper, every time. This meant she would have to sit down on the toilet, or squat in the woods, to minimize the mess left on her genitals. Girls simply had to embrace the lack of the male organs their bodies didn't have a need for. Instead of a penis or balls, Jeff, being a girl, had a vagina between her legs, a mere recepticle for whatever penis wanted to fill her uterus with sperm. She would be responsible for her uterus and her eggs, suffering the pain and misery of menstruation to make sure her body was ready to grow a child.
Jeff stood up and walked to the mirror. She saw Kara's beautiful face in the mirror. She took her tank top off and admired her flat, barely pubescent chest. Seeing her sister shirtless was a little creepy but this was what she had wished for. She pulled her pajama bottoms off and stared in shock at her new vulva. This really happened—she was a girl. She could do anything she wanted now. She turned to the side and looked at her new butt. She rubbed it, thinking of how perfectly female she looked. She was a naked 11-year-old girl and no one could stop her.
The most important thing, she suddenly realized, was waking up Kara. How would her new big brother react? She smiled at her reflection and put her clothes back on, and prepared to go see the teenage boy in the next room.