InsaneJournal

Fic: Rates of Change (Harry Potter, Katie/Alicia/Angelina, NC-17)
Title: Rates of Change
Author: celeria
Length: 1771 words
Pairing Threesome: Katie/Alicia/Angelina
Rating: NC-17
Warning: Just the threesome thing
Notes: Here we go again with the threesome-math-theme-girlsex thing. This sort of references my earlier fic Differential Equations, although you don't need to read one to understand the other. "Rate of change", in math, is generally either average rate of change or instantaneous rate of change, which is also known as a "limit."
Originally posted at pornish_pixies

Rates of Change

Katie doesn't expect them, exactly, but she isn't surprised when they come crawling into her bed well past midnight, parting the curtains and rustling the sheets so quietly that she senses them before she hears them. There is a little sound like a whisper, a kiss, a locking spell on the curtains, and then she feels hands and fingers and mouths on her arms and neck, licking at the place where her shirt dips off her shoulder, unwrapping her out of her pajamas in the dark. She wants to tell them to slow down, to ask what's going on, why they aren't drinking and celebrating their last night with the rest of the girls in their year, but Alicia's lips are already at her throat and Angelina's straddling her thigh, smoothing her fingers across Katie's stomach. Katie shivers a little, and then feels the wetness start too soon, along with the almost-painful sensation when she realizes her nipples are hard between Alicia's fingers.

She wants to tell Angelina to stop, that this is too quick, she's not ready for the way the dark fingers are snaking down her hips, drawing little circles and twists like question marks, finding the lines of the veins in her legs. And she's not ready for Alicia's mouth on her collarbone, on the small rise of her breast, the puckered nipple that stands out, taut, waiting to be kissed. Too soon, too soon, Angelina's kissing her knees, the place where a Bludger hit her in their last game, and now her thigh, that's the place where she has a birthmark that looks like a scab, too soon for Angelina's tongue to be tangled in her hair, moving over her clit, sliding firmly inside her. And Alicia must be taking her cues from Angelina, because now she's sucking on Katie's nipples, first one, then the other, alternating with teeth and fingers and fingernails that make Katie tremble, a whimpering shudder that starts low in her back and wiggles its way up along her spine.

"Too fast," Katie tries to say, but either her voice isn't working or they're not listening, because Alicia palms her breast, the heel of her hand rough from hours of flying and stirring a cauldron. Her other hand is against Katie's mouth, as if to close in any little cries that might encourage Alicia to stop what she's doing. And Angelina's diving deep inside her with her fingers, dark and strong and slightly scarred like the handle of her broom, licking her clit in small circles and lines. "Slow down," she wails, but they're not listening, and maybe it doesn't matter, because in a second she's coming, a rush of wet against Angelina's fingers, and her whispers and sighs against Alicia's.

It takes her a minute to gather her stomach and her head and her breath, and by the time she does Angelina's eased out of her, her fingers slick and shiny, and Alicia's kissing her cheeks and her eyelids and the hard muscle in her neck, gently now. She could swear she sees something pass between them, a shared smug grin, but it doesn't really register before Alicia starts kissing Angelina and she wants to be part of that, needs to feel someone's skin under her hands.

Alicia's pinning Angelina down on the bed, in an unusually demanding way, and Angelina squirms, makes a noise like she wants to get up, but Katie watches Alicia shake her head no. There's a frown between Angelina's eyebrows, a small furrow as thin and soft as her brows, but Alicia kisses her, a kiss so slow and languorous that Katie can feel herself getting wet again. Alicia's on all fours over Angelina's body, hands on either side of her ribs, knees woven with Angelina's, light and dark. Her tongue is moving down Angelina's sternum, then around her breast in circles that get smaller and smaller, slower and slower. Angelina makes a lovely noise and Katie grins, but Alicia just shakes her head. Katie can swear that that's the smile again, the smile that says Alicia knows exactly what Angelina wants and that she's not giving it to her.

Katie still isn't sure what she wants to do with herself, so she kneels and pushes a kiss from the small of Alicia's back up along her spine, then trails the flat of her hand over Alicia's ass. She can feel the muscles tensing in the gaps between her fingers, and for reassurance she kisses her some more, hips, sides, back, rear, thighs, the place where her leg muscles dip, concave. With her right arm she reaches up to stroke Alicia's stomach, her ribs, her breasts, and she can feel that smile taking over her own lips. Alicia takes her mouth away from Angelina's body long enough to make some nervous sounds, the same way she does sometimes in sleep when Katie's hands get too low on her body, but her legs are trembling next to Katie's, trying to hide the quiver between them.

Katie squeezes Alicia's nipple gently between her fingers, watching Alicia get back to Angelina's breasts. The dark thighs and cocoa-coloured stomach are clenching and unclenching below Alicia's body. Alicia puts her weight on her left hand and uses her right to draw tiny pictures over Angelina's nipple, in the dip of her belly button, across the bony socket of her hip. Katie runs her fingers over Alicia's nipple, then sits up on her knees so that she can touch both her breasts at once. Alicia makes a noise against Angelina's skin, much more receptive than anxious this time.

Alicia's back is a straight, cool plane of angles and untouched bare places. Katie brings her hands around from Alicia's hips and tummy to her back, down the flat of her ass, between her legs. Her fingers push into the soft crinkled skin and meet wetness, tightness, the crater below Alicia's dark brown pubic hair. Alicia sucks in her breath, concerned and ready all at once, and then she pushes her bottom toward Katie, giving Katie more room for her fingers, more of those depths and folds that she wants to explore. Above her – or is that below? – Alicia's moving down Angelina's body, still so delicately that both girls hear a muffled curse from the head of the bed. She feels it on her face – Katie grins – there's that smile again.

From this angle it's hard to find Alicia's clit, and Katie lets out a tiny grumble of frustration when she can't get Alicia into a good position. It's hard because Alicia's bending low over Angelina, nose to mound and tongue to cunt, back arched and graceful. Katie waits for Alicia to situate herself over Angelina's clit, and then with her fingers she spreads Alicia's wet lips and tucks her thumb inside her, moving over that little bundle of nerves. Alicia makes another noise, this one sweeter, a growl tempered with honey. Katie flicks her thumb over the spot and then forward, so that she can rub in circles over Alicia's clit.

Angelina's making her own noises, too, frustrated ones, half between anger and sobbing the way she was after their first Quidditch match with Ron Weasley as Keeper. For a moment Katie wonders why Alicia doesn't dive into her with fingers and teeth and tongue the way she usually does, because Alicia certainly knows what Angelina likes. And then she feels her thumb slide back into Alicia's wetness and she knows why.

Alicia's finally moved onto Angelina's clit, although from the way Angelina's whimpering, she must be using just her tongue, slowly, with kitten-shy licks and laps. Katie redoubles her efforts, thumbing the tiny nub, stroking the hood of Alicia's clitoris with just the end of her fingernail. Alicia's hips are moving in frantic, unsteady circles, nothing like the calculated way that she's tonguing Angelina's clit. Katie wishes that she had as much patience as Alicia seems to right now, but she doesn't, and so she speeds up, her fingerprints creating a rising hum, until she hears a strangled cry against Angelina's pubic hair and her thumb is locked between Alicia's legs, tight and red, her palm cupped against all the places that Alicia's soaking wet.

There are various kinds of threats and promises coming from the general vicinity of Katie's pillow, so Katie grins and takes her hand out of Alicia, wiping her fingers hastily on the sheets. She presses another kiss onto the muscled leg and watches as Alicia dips her tongue slowly into Angelina's viscous slickness, comes back out with a tongue tasting like salt and tartness – Katie knows, because she's done this to Angelina too. But never this slowly, and she wonders at Alicia's measured determination as she settles on Angelina's clit and kisses, sucks, finally raises the speed until Angelina's orgasm hits, shaking her thighs on either side of Alicia's face and making Katie's stomach feel warm and chilly all at once.

She expects both of them, or at least Angelina, to hurry back upstairs to their own dorm, to the merry-making that she can hear filtering down through the muggy June air, to their friends in their own year. But when she wakes in the middle of the night, to the sharp smell of sex and the fire-warmth of Angelina's skin and the lazy scent of Alicia's fingers, she sees that Alicia's hair has braided itself with hers and Angelina's wrapped around both of them, brown fingers making a bracelet around Alicia's wrist, dark cheek pressed against Katie's pale legs.

They don't talk about it at breakfast in the morning, over eggs and toast and Angelina and Alicia's last goblet of pumpkin juice in the Great Hall. And they don't talk about it while they pack, each in their separate little corners of their dorms and their minds. But they both kiss her on the way out, one on each cheek, and they end up in three separate carriages to go down to the Hogwarts Express, waving goodbye.

Katie wonders if she should feel sad, wonders if she should feel like she's lost something. She wonders what this means, if she means nothing to them, if they mean nothing to eachother. She wonders where this leaves her, the last and youngest Chaser, wonders what this means for next year, and all the changes for their Quidditch team.

She shoves her trunk into the carriage and climbs up, then turns to offer a hand up to Ginny Weasley, who's having some trouble with her own trunk. The small freckled hand grasps hers, and Katie smiles at her.

fin.