This is pure, unadulterated smut. I regret nothing. I also really like italics. Like, a lot.

I wrote this in maybe thirty minutes, and I should really be asleep right now but when the calling for some good ole' McCoy/Chekov lovin' comes knocking, you just don't turn that down. You just don't.

Edit: I've run back through it and edited bits and changed some stuff around now that I've had some sleep. So maybe it's a touch better now, and more accurate.

Warnings: SEX. GAY SEX. LOT'S OF IT. IN DETAIL. Also language.

-:-

It took approximately three seconds for Leonard McCoy to decide that Pavel Chekov's mouth should be fucking illegal.

Chekov had somehow seduced himself into McCoy's bed – or rather, between his knees – in record time. It took about two bats of his eyelashes, a murmured please doctor? followed by it's Russian counterpart, and a well-timed enlarging of his already far-too-big blue eyes. Life had well and truly chewed up McCoy and spit him back out for a tasty Russian to ravage.

He wasn't even fighting it.

But McCoy was a doctor, not a god damn saint. Those lips practically begged to have a cock placed between them, and the doctor would be lying if he said he hadn't thought about doing just that. Often. Probably too often. To be fair, he hadn't thought about any such thing until Chekov had turned nineteen, and started wearing these shirts around the ship in his off time that frankly shouldn't be allowed. He'd never been attracted to mesh before. Never. He'd never been attracted to Chekov before, either, but things changed.

McCoy hated change.

And now, because of mesh and blue eyes and change, those wide, pink lips were stretched around his thick cock and god damn his tongue was flickering and fluttering and laving all over him like he was an honest-to-god lollipop. He could be fucking grape flavored for all the enthusiasm Chekov was applying to his dick. It was delicious.

Oh, Lordy – Chekov had just swallowed him whole, working his throat around the cock in his mouth and he had suddenly started humming, some nonsensical little tune he'd probably heard from his mother. That humming was positively sinful-it was more than fair to say that Chekov had done this before, many times, and the thought sent something like jealousy stabbing through his chest. No, no-he couldn't, shouldn't think that way. This wasn't the twentieth century. Chekov could sleep with whoever he liked, as many times as he liked, as long as he was safe about it. McCoy was still a doctor, damnit.

He chanced a look down and groaned audibly. Chekov looked right at home between McCoy's thighs, cock stuffed down his throat and sucking McCoy's soul out through his dick.

Maybe he was. Maybe he had some secret soul-sucking blowjob power that he wasn't aware of. He should tell Jim about it.

And honestly, McCoy would let him suck his soul right out and then some if he just kept doing that right there-

Chekov pulled off his cock, raising his eyes to meet Leonard's, and he was practically glowing with content. McCoy maybe thought a nineteen-year-old ensign really shouldn't look so fucking right between a man's thighs, much less his, but he really did, and fuck if McCoy didn't want to keep him there all night. Or, better yet, throw him on the bed so he could plunge into that gorgeous, lean body –

"It is good, Doctor? I am pleasing you?" His voice was thick, throaty. Having swallowed a dick down your throat probably did that to you, McCoy mused.

"Fucking hell, kid, it's more than good. You know damn well it's good."

"Pavel," the boy licked the underside of his cock, then tongued off the translucent pre-come that had started leaking out of the tip. "My name is Pavel."

"Pavel, okay, yes," McCoy breathed without hesitation. He didn't call anyone by their first names except Jim, but Jim was an exception. Chekov-Pavel, well, he was an exception by proxy, he supposed. When a boy sucking your dick like it had never been sucked before asked you to call him by his given name, then you damn well did that.

"You are wanting to fuck me now, yes?" Pavel murmured, and McCoy's fingers clenched in that curly, dark blonde hair. Things like that should never come out of Pavel Chekov's mouth without a big fat warning to prepare people, because he suddenly felt like damning all caution and coming all over that doe-eyed face.

"Yeah...Pavel. I'm wanting to fuck you now," he growled, and Pavel grinned like a cat who caught the mouse. Before Leonard could blink Chekov was scrambling onto the bed and arranging his long limbs around until he was lying on his back, spread open and ready for Leonard's use.

It was fine art splayed out on his bed and McCoy suddenly never wanted Pavel to be anywhere else but right there, on those white standard-issue synthetic cotton cheets, waiting for McCoy to fuck the daylights out of him.

"You're gonna be the death of me," McCoy grumbled under his breath, but he wasted no time in moving to kneel between those skinny, endless legs. Pavel instantly wrapped them around his waist. McCoy felt like all the breath had left his body quite suddenly and would never come back.

"Doctor?"

"Pavel...you're so young, and smart, and god damn you're pretty, and you're more than I fucking deserve, but I really don't want you to leave."

"Doctor," Pavel purred, and McCoy realized his own hands were shaking, "I am not going anywhere. You think I am those things? Well, then you are strong, in your heart, and so handsome like an old movie star, and so sour I think you must be made of lemons sometimes. But I like you sour. I could not think of a better way to spend this night. Now," and here he wiggled his ass, and McCoy's vision swam with lust, "fuck me, Doctor. I am all ready, just for you."

McCoy furrowed his brow at those words. Ready? He reached a hand down to thumb at Pavel's entrance, and-ah. It was indeed slick and stretched. He quickly gripped Pavel's hips to keep from exploding with lust. The damn kid was ready for him, he had prepared for this. Oh, to be a young and eager lover...

"Are you sure you're ready?"

"Da, yes, please..."

"Hm." McCoy's fingers found that tight little puckered hole again. "I'd better make sure of that." A finger slipped in with little resistance. "Make sure you're stretched to my satisfaction." Another finger, some more resistance, and Pavel's breath hitched. "Doctor's orders."

"Oh..."

He pulled his fingers out and grabbed a bottle of lube from his bedside drawer. Whatever Chekov had used was already drying up, if the friction was anything to go by. He refused to hurt Pavel, no matter how desperate those little whimpers were starting to get. He wasn't a damned teenaged boy fumbling around in the dark so he could stick his dick into a warm body.

Three freshly lubed fingers slid back into a slick, welcoming heat. Pavel's answering moan was music to his ears. He leaned down, mouthing across Pavel's skinny neck and contemplating if he should leave any hickeys. Questions would be asked. "You ready for me?" McCoy muttered into Pavel's throat.

"Yes! Yes, doctor, please," Pavel groaned, eager for more.

"Perfect." He leaned away and fumbled for a condom out of the drawer. Hypos may have eliminated most of Earth's sexually transmitted diseases, but the alien ones were numerous and often latent. Medicine could only do so much against the vastness of the universe, and McCoy was nothing if not paranoid. He was always careful.

McCoy slid his eyes up to Pavel's. They locked, dark hazel on blue, as McCoy carefully slid into that tight, delicious heat. It was almost too much. A thrill of pleasure shot down his spine, causing his skin to pebble up into goose flesh.

"Lord, kid – Pavel," he groaned. He began to move with slow, steady thrusts that rocked Chekov back and forth. Chekov shifted, resting lean arms around McCoy's neck as he pulled himself up to McCoy's face, inches away, so that he could stare into his eyes. He didn't quite kiss him, just rested his forehead against McCoy's.

He was making the most delicious noises – breathy, tiny moans, sighing grunts that would edge into a whimper, and he'd occasionally clench his eyes shut and murmur something unintelligible in Russian.

"Doctor," he moaned suddenly, loudly on a particularly deep thrust, and McCoy shook his head.

"Leonard."

"Oh, Leonard! Please, there, again," he begged, mouth open and pink, and McCoy obliged, angling his body just so, hitting Chekov's prostate almost every time with deep, hard thrusts.

Pavel jerked beneath him, becoming a snake in his arms as he rutted against McCoy's body. It wouldn't be long before Pavel came, if he kept this pace.

True to thought, Pavel came shortly with a sharp cry. McCoy felt the sticky wetness on their abdomens and grimaced a bit. The sensation wasn't a totally pleasant one, but that could be overlooked for the image that Chekov presented. The sight of the boy's face, flushed with ecstasy, and that beautiful sound he'd made when he came, it was enough to nearly send McCoy over the edge. He completed a few more deep, purposeful thrusts, beginning to stagger as he neared completion.

But Pavel grabbed his hand just before he could and wriggled away so that McCoy slipped out of his body. Dismayed, McCoy could hardly come up with anything to say, but Pavel just held up a finger to his lips and winked. He slid the condom off with practiced ease and tossed it aside carelessly. He kneeled on hands and knees facing McCoy's cock once again and glanced up at him, eyes darkened and begging, and he said the most beautiful thing- "Come, Leonard. On my face."

That was it. He hastily jerked his cock a few times, still teetering so close to the edge, and he came so fast he saw spots dance across his eyes. White spurts of semen painted that lovely face, thoroughly debauching it, and McCoy knew whenever he saw the kid walking around the ship from now on all he would ever see was his own semen striping the kid's face.

It was almost too much for an old doctor to take.

He collapsed onto his side, winded, and Pavel followed him eagerly, still licking semen from his lips. He'd wiped the rest off with his discarded shirt, fished off the floor where it had fallen earlier. He curled kitten-like around McCoy's larger body as easily as if he had belonged there all this time. He wasn't sure how Pavel managed to find places to fit his gangly limbs.

"Doctor – Leonard – I would like to stay here. Sleep with you. Is it okay?"

How could he deny those eyes? Swallowing thickly, McCoy huffed to cover up his eagerness for Chekov to stay and shrugged. "Yeah, I suppose. Wouldn't want to kick you out bare-ass naked for the whole ship to see."

He may as well have said he'd marry him, what with the way Pavel's entire face lit up. Wet, slippery lips were pressed to his and he reacted on both instinct and choice, pressing back against those lips and slipping his tongue into that delicious mouth that tasted like his own semen. He'd never been into that before, but maybe now was a good time to start.

"Good night, Leonard. I will see you in the morning," Pavel murmured huskily after pulling away, only to bury his face into McCoy's throat.

He smiled into Pavel's hair. "Yeah. I bet you will, kid."