Emily's eyes narrow with spite. "Let's see how well you'd deal with things if you were in my shoes... If you were the little sister and I was the cruel older sibling making sure to humiliate and shame you as much as you did for me, hmm?"
A cold sweat runs through you. "Emily no, you can't! I'm not a girl. I- I'm your big brother! Please!" you stammer.
"Oh? Strange, I didn't think the term brother would apply to you, since you're so obviously a girl!" She giggles as you feel a wave of power run through you. "In fact, you're so girly that no one would ever mistake you for a boy!"
Reality warps and you feel a thrumming in the air as the room grows around you. You feel your once-wide shoulders narrow, becoming dainty and frail. The painful soreness in your muscles vanish, and you let out a sigh of relief, only to be replaced by the realisation that your lean muscles have dwindled and withered away, leaving you with the thin, stick-like arms of a weak girl.
Emily chuckles. "Hope you like struggling to open jars, or begging for the help of a boy!"
You hair cascades down your face, brushing delicately against your now-exposed shoulders, peeking out of your oversized t-shirt.
You can feel the changes in your face, your jaw turning soft and rounded, your nose becoming cute and button-like. There's a pleasant softness that blooms from your lips as you feel your neck turn slender and delicate. "What the...!?" you whimper, your voice having shot up several octaves, now sounding cutesy, soft and pathetic to you.
Powerless, you squeeze your dwindling hands into little fists. For sure, you'll now have a hard time commanding attention or respect with such a thin, girlish voice.
As your chest narrows, you feel a tingle draw your attention to your stiff nipples.
Reflexively, wrap your weak arms around your chest, knowing very well what is happening under your oversized shirt. You feel perky little mounds swell and push against your arms, brushing naughtily against the harsh fabric of your shirt.
As you look down at your budding breasts, you see your pants and boxers slide down your much narrower hips. A shameful blush burn your cheeks as you see your cock, erect and throbbing in full display before your sister.
Emily's glares at your exposed manhood, glistening with pearls of precum, her cheeks turning just as red as yours. "Well well well... I didn't know you were such an... endowed boy." she coos appreciatively, squirming slightly in her chair. "Had I known... Oh well. Too late for that I suppose. It's panties for you from now on 'big man'"
You gasp and moan as your cock trembles, disgorging thick ropes of cum. Again, and again, it fountains out of you and drips down your shaft and thighs, every spasm of your penis draining it of its size and girth.
Desperate, you clutch your dainty little hand around it, hoping you can keep it from dwindling away... But soon, it's too small to hold in any way other than between a few fingers... You sink to your knees, spasms of involuntary orgasms leave you quivering, turning your legs to cotton as you disgorge every single drop of male seed into your hands, down your legs and on the floor.
You mewl girlishly as you feel your empty balls retract inside you, boring deep between your thighs as your once-proud cock nestles atop your nascent lips as a cute, pink little button, swollen with pleasure and glistening softly with new, feminine juices. You can feel an emptiness blossom into you, your hips widen and your plump lips engorge with desire as you lose the last vestige of your male sex.
Gasping for breath and on all fours, you look up to see Emily staring at you with grim satisfaction, and perhaps a hint of lust. Her own nipples are poking obviously at her spagetti-strap top, her breathing quicker and shallower than it was before.
"Very cute." she grins. "You'll certainly draw the eyes of boys everywhere you go."
"Fuck you!" You squeal out in anger, your shamefully feminine voice making your rage sound like a petulant and childish tantrum.
Her smile vanishes and her eyes darken. "Fuck.... Me?" She takes a few menacing steps toward you as you shrink away from her,realizing what you said. "FUCK... ME?!" she repeats furiously.