...a schoolboy uniform from the closet. This uniform is only fit for a middle school boy around 11-13 years, but you know it's not gotta fit on your body. As for your girlfriend, she might fit in that uniform, plus she's always wanted to be a boy and wonder herself what is like to be a boy. And honestly, one time you accidentally caught your girlfriend wearing men's clothing after you entered the room. She was shy and embarrassed after getting caught by you, but you're not laughing at her or anything. You're okay with her having her own kinky. And even during sex, your girlfriend dresses up as a boy for roleplaying and thought it would be a fantasy gay sex. Now, she's about to try it out just to see if the transformation would work. First, you watch her take off her clothes and throw them on the floor as she reveals her perfectly naked feminine body. Your girlfriend can tell you enjoy the view as she smiles at you, then she takes the boy's briefs, heartbeat accelerating as she slips them on. Of course, it isn't easy, the uniform is tight on her body as she wears the tight pant almost there as it only reaches her butt, clearly not designed for the body of a young woman, slim as she was. No, these briefs were designed for a smaller, less shapely 13-14-year-old boy! "Dammit, get it there," she responds angrily.
"Babe, take an easy... I'm sure it will fit when the transformation starts," you reply. "But you should have tried different clothes, you know."
"I know, honey. But it would be interesting for us if we have a role-playing game with this." Wow, didn't your girlfriend be that kinky? While they were too tight all around, the pouch in the front stood sadly empty, since your girlfriend didn't have the dick and testicles right now to fill it up... She struggles to get into the dark blue short trousers, which were also a little ill-fitting on her thighs and ass, then she proceeds with the white button-up shirt. The sleeves proved to be too short for her arms, and although she tried to pull and stretch, there was no way she was going to button it up across her big firm, and sizeable boobs! She left it half open like this for now and tried on the shoes. They were too small and her feet weren't gonna fit in there...
The black tie and blue blazer were still there laying on the bed. Frustrated, Jenn took the glasses, put them on, and went to the mirror. She starts laughing at how ridiculous she looks, but to you, you don't think it's funny at all. You think it's cute when your girlfriend wearing boy's clothes, like a tomboy. And you can see a bit obscene with her naked breasts popping out of the almost fully unbuttoned shirt when she felt a tingling inside her chest. Suddenly, the tingling sensation started turning slightly painful too, as her body began changing and shrinking. You begin to stare at her body changing, mouth agape, and incredibly, in just under a minute she had completely transformed into a short 13-year-old boy with dark, closely cropped hair. So it's actually worked! Both you and her are pretty shocked, your girlfriend touches her flat male chest, her completely different face, she feels her now short hair and then... She takes a peek into her briefs! And there it is, predictably the ex-young woman is greeted by the sight of her new genitals. A perfectly normal penis and scrotum that belonged to a little boy who just entered puberty. The sure mark of her new gender. HIS new gender, better yet! Your girlfriend is now a BOY.
The new boy realizes that his uniform now fits him perfectly, so he decides to continue getting dressed. He put on his socks, and shoes, then he buttoned up his shirt neatly to the collar. The boy then takes the tie and he slaps his own forehead, remembering that your former girlfriend didn't know how to tie a tie! "Well, this sucks!" He said out loud, disappointed and frustrated, but then he got an idea. "Hey,... if you don't mind, would you help me out with the tie?"
"Okay, babe. Let me help you out." You get up out of bed and you come to him to help him tie it around, over, and then under. After that, you have done it and s/he is fiddling proudly with his knot and collar in the mirror. "Kewl! Nice job, bro!" He appreciated you.
"Thank you, 'kiddo'," you respond to her/him as you start to realize she is about to act like a little boy all a sudden. Well, that's probably nothing. Then after that, you and your BOY/girlfriend start...