Disclaimer: Not mine, absolutely none of it. Such a pity, because they'd have more fun if I was in charge. Ho hum.

Author's Notes: Written in response to Porn Battle VIII's prompt 'rough sex', and for recumbentgoat who asked for ass slapping.

Yours

She'd done it without thinking. Not that she regretted, but she could never have guessed what she was unleashing.

Really, it was entirely his own fault. If he was going to work in her room between make-out sessions (or mutually enjoyable acts of physical intimacy, as Spock liked to call it), then she was going to watch him. If he was going to stand and bend over the console instead of sitting, like any normal person, her eyes were going to travel over the pleasing definition of his strong, sculpted ass. And if he was going to stay in that position for any length of time, could she really be blamed for acting on impulse, just this once, and coming up behind him to smack that ass?

The whack was satisfyingly sharp. Her hand had landed squarely across his buttocks, and was sharp enough that he twitched, his whole body going stiff. Not hard enough to hurt – like she could hurt him if she tried.

When he turned his head ever so slowly, to look at her, she was chuckling. She thought she could laugh it off. But his dark eyes were dangerous.

"Explain," he said coolly.

Her smile was beginning to grow forced. "Your butt looks really good when you're bent over like that. I wanted to show my appreciation."

And there went the eyebrow, arching as he straightened slowly, turning smoothly to face her. Seldom did he make her feel so small, but with a single step towards her he suddenly seemed to tower over her. Uhura swallowed.

"I have found your buttocks arousing on numerous occasions, Nyota. I had not realised there was a standardised means of expressing appreciation for such beauty." He tilted his head slightly, black eyes momentarily flicking down – to her lips? To her breasts? She couldn't tell. "May I?"

It was the deepening of his voice that took her breath away. He had let slip signs of his arousal before, but usually mid-coitus, when his self-control had almost completely gone and he functioned solely on sensation. She had never known his voice communicate such lust during a normal conversation.

Uhura swallowed again, hitching a smile onto her lips, despite the fear mixed in with her arousal. "Sure," she said casually.

Spock stood aside, gesturing for her to take up his original position. She did so, palms flat on the warm console, legs slightly apart. She stared at the wall ahead, concentrating on the loud thud of her heart.

"When you lean forward in that manner," he said darkly, "as you so often do as you work, your skirt rides up slightly, and from a seated vantage point I can see your thighs. And your undergarments. Despite my quite considerable self control, I find myself inadvertently recalling the feel of your legs wrapped around my hips as we make love." Uhura bit her lip, feeling strangely exposed despite being fully dressed. She would swear she could feel his eyes on her. "And then you often shift – would you mind?" Uhura glanced back at him – standing as he always did, hands clasped behind his back, shoulders rigid, but his focus entirely aimed on the lower half of her body. Her breath hitching, she looked front again and shifted, almost out of habit, moving her body's weight onto one hip.

"Just like that," he murmured. "And my focus moves from your thighs ... to your buttocks. Which, really, serve little logical purpose, particularly where the copulative act is concerned. Yet I find them deeply arousing." This final admission was punctuated by a firm smack to her right ass cheek. Uhura gasped, jumping, weight moving onto her toes. The sudden heat of his hand, the brief glimpse of the lust over-powering his mind drew her breath out in a soft moan.

"I begin to understand this gesture of admiration," he said, voice increasingly thick. There was the sound of him shifting, gentle fingertips lifting her skirt then hooking in the waistband of her panties. "The limited pain and considerable surprise cause your body to tense, making this portion of your anatomy even more erotic." The underwear around her ankles, effectively holding her in place – as if she'd want to be anywhere else – Spock pressed a chaste kiss to the heated spot where he'd slapped her. Another quick flash of hot pain, on her other ass cheek, quickly gentled with a long lick.

She could feel him breathing against her skin, quick and sharp and ragged. "I find myself incredibly aroused, Nyota," he said, voice breaking and lips brushing over her sensitised skin. "Would you have any objections to my continuing with more direct sexual activities?"

"Please," Uhura groaned, her fingers grasped tight around the edge of the console.

His tongue was between her legs, hot and quick, pressing and exploring her most intimate areas. She cried out, slumping forwards onto the computer's surface as his tongue wriggled inside her pussy. "God, Spock," she moaned, eyes falling closed. Even over the deafening sound of her own breath and heart and the blood pounding in her ears, she heard his zipper and the rustle of his clothing. "Fuck me," she whispered, her breath steaming the glass top of the console.

Spock needed no further instruction. Within moments, he was filling her, hips working fast as he slapped her again. Uhura moaned hard when his hand slid over her back to hold the nape of her neck, pushing her down and forwards while his other hand gripped her hip harder than ever before. Distantly, through the pleasure and the pain and the intensity, she thought that she would be bruised in the morning. Beyond all this, Spock was growling and pounding into her. In the harsh Vulcan tongue that was his native dialect, he commanded her to come – and Uhura knew better that to do anything but obey.

Distantly, as her orgasm rocked her, hips jerking in his painfully tight grip, she felt his rhythm speed and grow erratic. Leaning forward over her, he bit down on her neck, marking her where everyone would see. He twitched inside of her, as breath that he must have been holding was expelled across her throat in a single growled syllable, "Mine."

Uhura shuddered at the implications. He began to relax over her, and she turned her head to kiss him. Softly, looking into his already mellowing eyes, she agreed, "Yours."