Their first time is... chaotic. Not a disaster, okay? Allison knows disasters, had Johnny Wilson (aka Braceface Johnny) try to go down on her once in San Fran when they were going out. That had been kind of a disaster (not that anything had happened, they'd just gotten sort of freaked out about it and after calming down they'd decided to just watch a movie instead). This is just messy. Just a tangle of limbs and snickers when Scott and Stiles keep accidentally (and then not so accidentally because sometimes Allison thinks they are still ten year old kids) tickling the insides of each other's knees.
They are on her bed, because it's the only one big enough to host the three of them somewhat comfortably, since she's 'tall and leggy, like a runway model' (Stiles' words) and Stiles is miles and miles of uncoordinated flailing limbs (Stiles' words) and Scott is nicely filled out and... uh, proportionate. Very nicely proportionate. All over. (Also Stiles' words.)
They have the house to themselves for the night because Allison's parents have business to take care of ("business, important business" her mom had said seriously, drawing out the word as she peeled some potatoes with her eyes fixed on Allison in an intense and meaningful gaze) out of town, and they've allowed her to stay because she'd told them was gonna hang out with Scott and Stiles anyway, whom they still firmly believe to be enough of a third-wheel to ensure she won't be having sex with her boyfriend.
Allison isn't about to correct their erroneous assumptions, and doesn't feel much guilt over lying to them by omission, since she is still a little pissed at them for hiding information from her all these years (she tries to make it cutesy to them, to let out these tiny jabs, throwaway comments that can pass for humor and still let her take out her frustration at them without having to get in outright shouting matches with slammed doors).
So they have the house for themselves, they can be loud and careless, and they are, but not in the most traditional of ways. Stiles almost elbows Scott on the face and Allison knees Stiles on his soft stomach ("oh God, sorry, sorry, sorry"), and there's more giggling than she had anticipated. And they also break her new lamp.
"Seriously?" Stiles says from where he's lying on the floor, the lamp bare inches away from his naked frame.
"Oh my God, Stiles, are you okay?" Scott asks, brown eyes worried and wide and Stiles is glaring daggers at him and... well, Allison can't help but to collapse on her back and burst out laughing.
They do get it right, after a few tries, though. The three of them all over each other, sticking together, backs to chests, one of Scott's hands on her breasts, playing with her pink, oversensitive nipple and the other on Stiles' hip; the fingers on one of Stiles' hands snug inside her, long and thrusting and making her buck and gasp into Scott's mouth while Stiles kisses the back of her neck.
Then it's some more logistics (which Stiles takes very seriously) and some more quick, messy shifting until they can find a position where Scott can comfortably slip into Allison, fucking her with a leisurely, maddening pace, and sloppily suck Stiles off at the same time.
Allison's orgasm is almost overwhelming, hits her like a freight train after Stiles' dick slids out of Scott's mouth with an obscene pop and he comes all over Scott's face ("sorry, dude," Stiles grunts, voice raspy and Scott takes one of his hands off Allison's hips to slap his ass and says, "you're a douche, man") when one of Stiles' hands drifts down to where she's all wet heat and rubs two of his fingers carefully over her clit, and then in a circle motion, just the way she likes it.
"Come on, Allison," Stiles urges her and Scott thrusts deeply inside, and brings one of his hands to her face, pushing a strand of hair away from her eyes and echoes Stiles' come on.
And Allison does. She grips Scott's hips and her bed's duvet and gasps and draws her legs up and lifts her own hips off the bed, meeting one of Scott's (now erratic) thrusts and oh.
Oh.
Stiles kisses Scott, licks the come off his face and says, "come on, you too" and Scott just follows.
"Wow," Allison says after they are done, cuddled against Scott's chest, with Stiles on her other side, one leg draped over them both and one hand tracing lazy figures on Scott's side.
"I know!" Stiles replies. "We are awesome at this."
"We are," Scott says, and his eyes are crinkled, soft and loving. Allison leans in to kiss him and Stiles awwws at them obnoxiously.
Allison elbows him.
And then shifts a little and cranes her neck towards him, says "c'mere", and kisses him too.
(They are awesome at this, really, and they only keep getting better with time.
On Allison's birthday Stiles goes down on her for an insane amount of time, mouth going red and abused as he eats her out until she's squirming with her hand on his head, yanking at his hair, the intensity making her buck against him, his pink tongue fucking into her, a drilling pace and then a tortuously slow one; circling her clit teasingly, using the flat of it to get her even wetter while Scott fucks him, chest against his back, slow and hard, hands firm on his waist and keeping him in place just the way Stiles likes him to, and just the way Allison likes to watch them go.
It's intense and so, so good.
Stiles and Scott are panting heavily by the time they are done, give each other a celebratory high five before dropping onto the bed, and Allison is too much of a boneless mess to react with anything other than a tiny, lazy smile.)
