Greatest Game/Dannie/Powers/Rodger/change first, aware
You decide to transform Rodger into Regina first, before going over. You focus on the idea of the 18 year old guy who insisted upon being your boyfriend while you decided on allowing it turning into an 10 year old version of himself, flipping the age difference to be in your favor. Only, of course, there's one key difference you made. The genders were reversed as well.
Ok, let's use this to test exactly how far your powers go. You concentrate on the idea that "Regina" has been this way for about 20 minutes now, and has been hiding herself in her room debating how to figure out what to do about school. Also, her parents have already left the house. With these ideas in mind, you give another thought and suddenly you are standing in front of the front door to Regina's house with a pleased smile on your face. In a move you feel is an absolute stroke of genius, the door opens in front of you and the nervous head of a 10 year old who looks for all the world to be a boy peeks out and looks around before her eyes go as big as saucers as she sees you.
"Dannie!" Her voice cracks in her shock at seeing you.
"Hi there Regina." You say, walking up to her with a giant smile on your face as you elbow your way in through the door.
"What!? Regina!?" She stutters in surprise at hearing the feminization of her own name, and then trips as she's back-pedaling back into her house with a heavy thud onto her butt. The culprit of her unsteady footwork is immediately obvious when her oversized T-shirt flips up to show the way too large jeans pinned to her waist by a belt that's wrapped several loops tighter than normal. The baggy pants go way too far down, and just about hide her bare feet as she stares helplessly down her legs.
You step in through the door and close and lock it behind you. "Are you Ok?" You ask her as you reach down and easily scoop her up into your arms as you carry her off princess style into her room. Meanwhile, your cock is absolutely throbbing and begging you to rip her pants off and pillage the sweet little hole beneath the oversized garment.
Regina hisses and gives a grumbled "yeah" in response, and then seems to suddenly realize what's going on as she looks up at you. "But! What are you doing here!? And..." She looks back down at her body as though she's debating about how to say what she's about to say. This is just the chance you were looking for.
"Well, I was thinking about what you said about us having sex and, well, I decided that I think I'm ready to do it." You tell her.
"What!?" Regina says. "I can't have sex! I'm a girl!" She blurts out.
"Oh, so it was fine when I was a girl and you were a guy?" You ask her.
"What!? No! Umm... wait, how did you!?" She asks as you toss her onto her bed and go to work on her belt buckle and pull those oversize pants down, revealing the child's sweet naked legs and tight hairless slit underneath. "Ahh!" She responds, reaching uselessly for her pants and then finally winds up just staring dumbly up at you. "Uhh... you don't happen to have a penis now, do you?" She asks with a twinge of fear in her voice.
"Yep, sure do!" You answer and shove down your underwear and step out of them before lifting the front of your skirt to reveal the thin 5 inch dick sticking up proudly from between your legs.
"What!? How... how is this happening!?" She asks, completely aghast as you climb up between her legs and start to lean down to start lining up your dick. "Ahh!" Regina suddenly stirs into motion as she tries to close her legs, but is stopped by your knees that are already between them. Then, she starts trying to back away and puts one hand over her crotch. "Ah! No! I'm too young!" She says. "I turned into a little girl!"
"Isn't that about the same thing I said too?" You ask her. "I thought age doesn't matter, this is what boyfriends and girlfriends prove they love each other." You say with a grin. "I'm only 4 years older than you." You add. "That's the same amount older than me you were before."
"Dannie, what!?" She responds with a dumbfounded look on her face. Meanwhile, you push her legs apart with your knees and lean down over her, pull her hand off her pussy with one hand, then line your dick up with the other before you push it in and enter her. "Ow!" She yelps as you slide your dick home inside her. Being a virgin yourself, and also very new to the whole having a dick thing to the point that you've never even cum as a guy before, you barely manage to last until you get the entire thing inside her before you groan and feel the sperm pulsing down your dick in warm spurts.
You groan and lay your head down next to Regina's nestling your nose into her neck. You can feel her reach a hand up to get your hair out of her face. Your amazing first orgasm as a boy just goes on and on, you can feel the thick white stuff going inside her to find the egg you have already made sure is waiting inside her 10 year old uterus. You have no experience orgasming as a boy, so you have no point of reference to realize this is going on two or three times longer than when the average guy masturbates himself. For you, this is just about as long as a really good session of pleasuring yourself as a girl. About the only thing unusual about it is that you didn't really have to do much more than stick it inside her tight and moist little hole as you think about how guys sure have it lucky.
The entire time, Regina remains in a shocked state of silence as you are filling her baby-hole full of your semen. After you finish, the fog clears from your mind a bit. Sure, it was payback to teach her a lesson, but you also just basically barged into Regina's house, ripped off her pants, and then raped her. The shocked silence from her continuing with her soft but strained breathing being the only sound she makes is definitely not making you feel any less guilty about it either.