As the energy pulsing through you builds up, your clothes seem to vanish, leaving you naked as the day you were born in the vortex. You can only see the strange swirling reflective surface that flows around you and, faintly, your own form through it, like staring into a pane of glass and seeing it slightly mirror its surroundings.
Slowly, before your eyes, your body transforms. You see and feel yourself convulse and change like a werewolf transformation in a horror movie, but strangely you feel no pain. Instead, it feels weirdly... pleasurable. Your body is surging with hormones, male ones giving way to female ones which displace them and reshape you, and they comfort you with endorphins and pheromones that are irresistible to the primal part of your mind.
Most of the initial changes seem to blend together, as you shrink down, your muscles turn more petite, your figure slims and your hips widen, your facial features turn softer and your skin turns smoother as much of your body hair thins or vanishes. This feels more like a weird kind of manicure than your sex getting inverted, and you kinda like how it feels to figuratively have the rough edges sanded off you. If anything, you feel like you look... sexy. Wow, are you really getting turned on by your own body?
Speaking of getting turned on, the changes reach your sex characteristics and almost instantly things start to become very different. You feel acutely aware of your nipples all of a sudden, as they surge in sensitiveness and you see the small nubs on your chest protruding, widening, turning pebbled. Your sexuality and desires are shifting too- you imagine having them touched, pinched, licked, sucked, and the concept arouses you. A lot. Curiously you rub them, and notice your voice has increased in pitch. You continue to touch them and stroke your cock as flesh expands on your chest, and you realise you're growing breasts. When your hand carefully cups the tender flesh, you moan eagerly, imagining larger, firmer hands than your own playing with them.
Before long you feel a warmth and pulsing in your crotch and peer past your newly formed boobs to see your cock shoot thick cum into the void. Once you've released what feels like every drop of your seed, the most masculine part of you is finally subsumed by the changes. Your shaft gradually shrinks, not simply your erection wilting but your penis receding away. Your testicles are pulled up inside your body and your scrotum tucks inwards to reshape from a sac into lips.
As all of this occurs, the feminine hormones assert themselves and you feel something you can only describe in one word. Emasculation. Not in the sense of getting weakened, just in the sense that you can tell you are not a boy anymore but a girl. The intrinsic identities you've always known transpose in your head- he turns to she, male turns to female, manhood turns to womanhood. And as what was once your penis finishes turning into a sensitive clitoris and your vaginal slit opens up, you feel a weird sort of euphoria about your new self.
Everything turns white after that, and you awake lying on a bed. Sitting up, you recognise the room and start to freak out in your head. You get up and walk to the mirror on your closet door, and your eyes widen as you see yourself- while your hands fly to cover her naked form. You're Amber now!
Hastily pulling on some underwear and a sundress, the first clothes you find in her room, you poke your head out the door and notice something weird. Your old room has vanished. Not only are you Amber, she's an only child now! You wonder what the fuck to do, and decide looking into her sleepover might be a good place to start...