She stretches you into something

Before you can protest, her other hand comes up. You feel her fingers probing at your face, and then—oh god—she pinches your tongue between thumb and forefinger and pulls.

The sensation is indescribable. Your tongue stretches out of your mouth like taffy, elongating impossibly, and there's no pain—just a weird, elastic pressure and the horrifying awareness that your body is being fundamentally reshaped. You try to scream, but with your tongue pulled taut, all that comes out is a muffled, pathetic whine.

"Holy shit, this is amazing," your sister breathes, genuine wonder in her voice. She keeps pulling, and your tongue stretches longer, longer, a pink ribbon of flesh extending two feet, three feet from your mouth. She starts wrapping it around your body like she's winding yarn, looping it around your torso, your arms, your legs.

You squirm and thrash, but her grip is absolute. Each loop of your own tongue binds you tighter, constricting around your limbs. The sensation is surreal—you can feel every inch of your stretched tongue, the texture of your own skin against it, the pressure of it tightening. She works methodically, almost artistically, wrapping and tucking until you're completely cocooned in your own flesh.

When she's done, you're barely recognizable as human. You look more like a small, pink bundle of rope, your features obscured, only your eyes visible through a gap in the wrappings. Your stretched tongue holds you in a tight ball, and when you try to move, you just rock slightly, completely helpless.

"Perfect," your sister says, holding you up to admire her handiwork. "You know, I was going to change you back after an hour or so, but this is too good. I think I'll leave you like this for a while. Let you really appreciate the situation."

She carries you across the bathroom, and you watch the world bounce past—the sink, the mirror reflecting your grotesque new form, the shower curtain. She pulls the curtain aside and sets you down on the shower floor, the textured surface cold and rough against your bound body.

"Mom's going to shower in a bit," your sister says casually, straightening up. "She has no idea you're in here, obviously. Should be interesting." She grins down at you one more time, then turns and walks away. The bathroom door closes behind her with a boom that shakes your entire world.