Kirk understands now why people were so seethingly pissed at him back at the Academy. He made short work of Starfleet's laborious academic program, sailing through the three year program in just under two, able to start and finish the training program - including the completion of the Kobayashi Maru, no matter how questionable his methods - in only one. He can remember the grumbling of his fellow cadets: "Thinks he's so fucking smart," and "Thinks he knows everything, the smug bastard."
He gets it now. Because now he has a Vulcan as his first officer, and the man couldn't be more of a smug, brilliant jackass if he tried. He's damn near unflappable and so devoted to his precious logic that sometimes Kirk just wants to throttle him. Or fuck him, but Spock won't have any of that on the bridge, so he's limited to seething, snarling, and occasionally slamming his fist down on the console and waiting on the fucking until later.
Today has been one of those days, and he's grateful the crew has signed off for the night. He watches in not-quite-sulking silence as Spock organizes a series of reports and formulas on his data pad, one hand distractedly bringing up his transmissions monitor. He's surprised when he recognizes the coordinates, when the viewscreen comes suddenly to life with the image of Sarek.
"Father," Spock nods respectfully before launching into his report. He and McCoy have been tracking down a mineral used in Vulcan painkillers and sedatives, a mineral which used to be abundant on Vulcan and is nowhere to be found on the newly colonized planet. They haven't yet found a duplicate, but Spock and McCoy are getting closer and closer to an adequate replacement.
They speak as if Kirk isn't even in the room, and he realizes it's because of the positioning of the viewscreen. The captain's chair isn't visible to Sarek - in fact, probably the only thing he can see is his son from the shoulders up.
Kirk's face is suddenly transformed from sulking to a shit-eating grin. He slides noiselessly out of his chair, crawling to where Spock has been standing and giving his report.
"The chemical structure is not unlike acetylsalicylic acid," Spock is telling his father. "It is a stable carbon-hydrogen-oxygen compound with the addition of-"
Here Spock stutters, not because he's forgotten the added elements, but because Kirk has settled on his haunches behind him and is reaching around him to undo his utility belt.
"Spock?" comes the distantly severe voice of Sarek, and Kirk presses a grin into the back of Spock's thigh.
Spock clears his throat carefully. "Apologies," is all he offers, hands grabbing Kirk's around the wrists with bruising force. "As I was saying, in addition to the three previous elements, there are additional traces of-"
But Kirk isn't listening. He lets his hands go slack as if submitting to Spock's will, and the moment the other man's grip loosens he deftly unfastens the front of his trousers, pulling them down just enough to expose his backside.
Spock doesn't stutter in his explanation this time, merely attempts to grab his hands again, but he's already wrapped them around his thighs in such a way that Spock would have to squirm or bend down to pry him off, and he won't do that when he's talking to his father for fear of looking too human. He presses his face to Spock's lower back, scraping his teeth there just enough to get his attention, feeling the muscles in his thighs ripple and shift.
"Acetylsalicylic acid is found in organic life forms," Sarek is pointing out evenly, apparently blind to his son's sudden distraction. Kirk takes a moment to suck his index finger into his mouth before teasingly tracing it down Spock's back, through the curves of his ass, teasing over his entrance.
Spock disguises a gasp as a particularly passionate response to the conversation. "The addition of nitrogen creates an inert compound unable to sustain itself." Kirk starts rubbing along the sensitive skin, slowly working his finger around the tight muscle there, impressed at the utter immobility of the stiff, stoic Vulcan.
"Then the compound cannot be grown or developed on New Vulcan," Sarek mutters with what passes for disappointment in his voice. He's even less emotive than Spock, which is saying something.
"No," Spock replies, and if there's a slight whimper in the word then Sarek doesn't appear to notice. Kirk presses into him then, the first joint of his finger slipping into him with little resistance. He can see Spock's feet shifting in his boots, the toes curling and uncurling as he tries to keep his composure. "But the substance may be able to be replicated on a large scale."
Kirk twists his finger a bit, leaning in to lick at the skin where his body connects to Spock's, equal parts trying to relax him and drive him out of his mind. "Replication could not be an option at this stage in the process," Sarek murmurs with a touch of disbelief.
"No," he says again, and the muscles twitch and ripple around Kirk's finger, loosening enough for him to drive in further. "But we are... close," and there's just a hint of hysteria in that word, "close to having it stable enough to attempt replication without compromising the integrity of the substance."
Sarek's voice turns a little more severe. "Are you unwell, Spock?"
Kirk buries another grin in the small of Spock's back, pulling his finger back just enough to make him think he's going to stop teasing. "I am quite-" he doesn't quite yelp when Kirk thrusts it smoothly back into him, and he must have hit his prostate for him to be losing it like that, "-well, Father."
Sarek sounds unconvinced. "You may want to request that Dr. McCoy look into possible side effects of the drug before you attempt replication. You may have been working too closely with a substance unsuitable for your physiology."
"I will discuss the matter with him promptly," Spock promises, the evenness of his voice betrayed the small line of sweat trickling down his back while Kirk massages relentlessly at his prostate. "Thank you for your time, Father."
"Live long and prosper." Kirk hears the high-pitched blip of the viewscreen being turned off and he starts working another finger into him.
"Is there any reason," Spock manages to rasp out, fingers grasping and digging into his console, "that this could not have waited until after my report to my father?"
"Sure. It wouldn't have been near as much fun." He has Spock stretched and relaxed enough for both fingers now, thrusting them into him with a lazy sort of rhythm. "And anyway, you did fine. I'd've been moaning halfway through explaining about the elemental structure if it were me."
"If it were you," and he inhales sharply on a sudden twist of fingers inside him, "I would never be so foolish as to distract you in such a fashion."
"Which is why you're the science officer and I'm the captain." He rises from his kneeling position, keeping Spock firmly impaled on his fingers and using his free hand to undo the front of his own pants. "Because you've got the composure to rattle off compound names to your father whereas I've got more important things to do."
"Your current display of blatant disregard for common decency suggests otherwise." And for all Spock's verbal objections, it's not as though he's trying to get away, shifting back eagerly into Kirk's fingers and making a nearly inaudible keening sound when Kirk pulls them out of him.
"I disagree," he murmurs, pressing his cock up against him and pushing in slowly, one arm pressed up against Spock's, fingers lacing with his on the console. "This is very important work, here." His free hand smooths over the fabric of his uniform, over the inch or two of bare skin at his stomach, and wraps around his cock.
"Indeed?" Spock says distantly, closing his eyes and letting his head drop forward.
"Almost as important as the science officer's work," Kirk mutters against his neck. He leans forward as he starts a deep, relentless rhythm. "What's the compound for acetylsalicylic acid again?" he whispers in his ear.
"Nnn," Spock whimpers, and Kirk can't tell if it's a repressed moan or just Spock trying to collect his thoughts. "C nine, H eight, O four."
"Right." He rewards the correct answer by picking up the pace, rubbing his thumb along the side of his cock. "How about naproxen?"
Spock shudders against him, alternately thrusting forward into Kirk's hand and back into his cock. "C... C twelve-"
"Fourteen," Kirk corrects him, sinking his teeth into his shoulder.
"C fourteen," Spock starts again, gasping a little, "H fourteen, O three."
"Good," Kirk purrs, thrusting into him at a deeper angle, loving the mewl it tears from his throat. "Peroxicam."
Spock groans. "Can't..."
He hears Spock drag in a ragged breath before he begins. "C fifteen, H thirteen, N three..."
"Almost there." And it's urging Spock on as well as a warning.
He seems to take almost half a minute to reign in his slowly shattering thought processes, one hand joining Kirk's on his cock. "N three, O four, S..." And the last is a hiss of pleasure as they lose themselves, Spock coming over their joined fingers as Kirk thrusts once, twice more into him before he's just as undone, burying his face in the crook of Spock's neck.
He's trying to get his breathing under control when Spock lifts both hands to his face, pressing a kiss in the middle of the mess in Kirk's hand and then slowly licking it clean. Kirk shudders at the display, pressing closer against him as his spent cock twitches faintly in renewed interest. "Bed," he mutters. "Before the night crew gets here and sees us."
Spock doesn't so much grin, but his eyebrows twitch in that vaguely evil, amused expression he often uses with Kirk. "What objection can they have to the science officer reporting his findings on anti-inflammatory compounds to the Captain?"
Kirk chuckles. "Well there's the part where you're doing it with your pants down and the Captain fucking you."
Spock has the decency to flush faintly green. "Indeed."