Disclaimer: I don't own Harry Potter or any of its contents, and I'm not making any money off this.
A/N: This isn't properly British.
Neville's excuse dies on his tongue. He didn't think it out properly, but it doesn't matter—on the second repeated/mumbled word, Seamus and Dean lose interest and disappear through the dormitory door. Neville doesn't usually go with them on Hogsmeade trips anyway; they were probably only being polite, since he's clearly been standing here all day with nothing better to do.
He gives a similar no-thanks to Ron, who's 'going to study in the library' with Hermione. Ron's awkward attempt at courtesy is a lot more obvious than Seamus' and Dean's. Ron visibly sighs in relief when Neville declines.
Then Neville's left alone in the doorway. When it opens again, Neville shuffles back, ready, this time. He knows who it is by process of elimination. He makes as if he was just leaving and bumps into Harry accidentally. (On purpose.)
Harry stumbles back a step, and the door swings shut behind him. He grunts a, "Sorry," and pats off his Quidditch robes. Out practicing all day, then. Neville mirrors the apology, and Harry smiles vaguely at him.
Neville grabs Harry's arm before Harry can move and Neville opens his mouth. Then he loses his nerve, closes it again, and lets go. Harry doesn't move and asks, "What?"
Neville nods upwards pointedly. Then turns a little pink and doesn't say anything. Ridiculously stupid plan, anyway. The house elves were probably just playing a joke or put it in the wrong place by mistake.
Either way, it's completely ludicrous for Neville to stay here all day, hoping to catch Harry, perfect, handsome Harry. Harry Potter, the golden boy, the Chose One, the pride of Gryffindor and the perfect Seeker and perfect friend and the perfect crush for all the common people. Like Neville. Neville's a nothing, and a ball of trembling not-good-enough cells, but he summons all of his Gryffindor strength (however deeply buried it might be) and tries to keep it together.
Harry's scrunching up his face and mutters, "Mistletoe?" in surprise and awkward confusion. As soon as he looks back down, Neville takes his chance. He's a bumbling idiot anyway; no one cares what he does, and even if word gets around, he'll do something even worse next week that'll cover this up. He leans forward to peck Harry lightly. He aims for Harry's cheek, but somehow ends up lip-to-lip, just lightly.
Harry slams him so hard into the wall Neville almost sees stars. His head hits the stone with a sickening crack, his back flattens into the cold, unforgiving surface, and Harry's strong, Quidditch-toned, warm body presses into his front. Neville's too stunned to do anything with his arms.
Despite a total lack of experience, Neville's eyes fall closed on instinct. Harry's head is slightly tilted, and their noses are touching, but not bumping, and Harry's lips are surprisingly soft. Harry's fingers tentatively brush Neville's sides, holding onto his hips, and holding Neville still against the wall. Then Harry's tongue snakes out, and Neville parts his lips by way of a moan. He opens wider once Harry's in, once Harry's exploring him, and Neville experimentally moves his tongue against Harry's. They battle for a moment, and Neville loses, and Harry explores his mouth hungrily, needy, rough and hot and downright sexy. Neville's hands brush at Harry's waist, finally moving, wanting to touch more. Harry kisses him so deeply that Neville's quickly running out of oxygen.
He doesn't want to part, though, not ever. He fists his hands in Harry's Quidditch sweater and moans as their teeth bump and their tongues fight and their lips swap sets of saliva. Harry smells earthy and sweaty and windswept and masculine. Harry grinds gently against him, and his tongue is contrastingly brutal, fucking Neville's mouth with a fierceness that makes Neville shiver in ecstasy. His head is swimming, and his body's on fire. Rapture's clawing in every corner of his being—if this goes any longer he might explode.
When Harry finally moves back, they're both panting. Neville physically sags with the loss. His eyes flutter half-open, and Harry looks similarly surprised and blown away. His cheeks are also a little pink, breath also a struggle.
Harry pulls his wand out of his pocket, and, without looking away from Neville, spells down the mistletoe. "Better get rid of this before Ron walks in," Harry mutters, and Neville's not quite sure how to take that.
He follows Harry over to the beds; Harry clutches the mistletoe tightly.