Notes: So. This is a thing that happened. First time writing Sebastian/this ship, so I'd love to know what you think.
Of all the distractions that Alec's new position held, Sebastian had to be one of the worst ones.
Despite his distrust, Alec had given him clearance for missions almost as soon as he'd taken over and since that moment, he was suddenly everywhere. Everyone else seemed to find him charming and the more Alec tried to avoid him, the more persistent he got and giving him the position as Head of security seemed to be the best decision if Alec wanted to keep a close eye on him and not have him try and be helpful at every opportunity he got. Most of the local Shadowhunters had accepted the change of power easily enough, but Alec still preferred to keep everyone he didn't know too well either at a distance or right in his line of sight; if the only way to do it was to assign everyone – including the newcomer – a particular position, then so be it.
What his carefully crafted plan hadn't included was having the man take his new job seriously enough to be as thorough with it as possible and report back with anything that seemed out of order. It was perplexing and the questions it raised were enough to drive Alec to frustration and distract him from everything that could be happening under the surface.
So he wasn't exactly surprised when, one night after a lengthier version of one of the newly established routine checks of the Institute's camera feed, he found himself backed up into Sebastian's desk, the man's lips pressed against his with the same insistence that seemed to colour his every gesture. It made sense in a way and Alec almost had the urge to laugh. Maybe Izzy was right and he was too suspicious sometimes; if this was all Sebastian had wanted, then most of his fears would prove unfounded. What took him by surprise was his own response, almost as enthusiastic now that, after all the time he'd spent trying to solve the puzzle in front of him, he finally had a semblance of an answer.
Sebastian's skin was hot, almost feverishly so when Alec reached up to trail a finger over his jawline and the rune on his neck, following the same line with his lips and grinning at the breathy whimper that the gesture produced. Ever since Sebastian's arrival, Alec hadn't been able to shake off the feeling that he was always one step ahead of him and taking him by surprise was even more satisfying exactly because of that. The feeling didn't last long; almost immediately, Sebastian's hands wandered down his chest, only stopping to undo Alec's belt and flick open the button of his jeans, tilting his head slightly to kiss him again.
Their eyes met for a split second as Alec detached himself from Sebastian's neck and the fleeting look of triumph in his eyes was almost startling; enough for Alec to stand on edge again but not enough for him to pull away. He let himself be drawn into another kiss, Sebastian's teeth grazing over his tongue in a way that should have been off-putting but wasn't.
"Lift up." Sebastian's voice was as casual as it had been when he'd given Alec his daily report less than an hour ago and Alec complied, pulling away from the desk, breath hitching as his jeans were decisively pushed down his thighs. "I can stop if you want me to."
"No." Alec was acutely aware of the fact that it was all in his hands now, but backing down didn't seem like an option anymore. He wanted this, he realised, he had for a while, and the challenge in the look Sebastian was giving him only spurred him on further. There was something about him that had drawn Alec's attention from the first moment and – for better or for worse – the feeling hadn't gone away. "No, you don't have to." Already tired of Sebastian's incessant attempts to take over the situation, Alec gripped him by his hips and turned them around, reversing their positions in one swift move. Sebastian's sharp features twisted into a smile and his fingers tangled in Alec's hair, dragging him closer and into another kiss as he thrust up, starting a rhythm that sent a full body shiver through Alec. It was what forced him into action; his hands pushing Sebastian's shirt out of the way on their own volition before he could undo the rest of his gear.
"That's it." The elation in Sebastian's voice was exhilarating and he gasped at Alec's first tentative stroke over his cock. Long, thin fingers curled around his wrist a moment later and he froze, eyes searching the man's face in a question he didn't know how to express. "Let me," Sebastian continued, his smile turning wicked as his other hand disentangled from Alec's hair only to be pressed against his lips.
It was unexpected; the intimacy that the gesture brought with itself, but Alec didn't hesitate. He had long since figured out what he wanted and all Sebastian had been doing was pressing him to just take it. There was no point in resisting now.
Sebastian's eyes slid closed in something resembling bliss as Alec took his fingers into his mouth and he felt inordinately pleased by that – he had yet to see a genuine reaction to anything from him and if this was as close as he would get, Alec intended on making the most of it. He wasn't given too long to process it; the next thing he knew, Sebastian's hand was wrapped around both of them and it was Alec's turn to almost lose his footing, the sudden wave of pleasure almost too much to take in. It felt better than anything he could have imagined; the pressure of Sebastian's cock pressed against his and those clever fingers squeezing just right on the upstroke. His expression was determined and his eyes were still focused on Alec's face with intensity that would have been frightening if it hadn't been so good.
As it was, Alec braced his hands on the desk on both sides of Sebastian's body, effectively trapping him in place. He didn't seem to mind – not if his quickening pace was anything to go by – and he groaned when Alec buried his face in his neck again, the previous kisses turning into bites that were sure to leave bruises. Sensitive spot, then. The knowledge made him feel confident enough to continue using it to his advantage and, as Sebastian's movements started growing even more erratic, Alec bit down on his shoulder harder than he'd intended to and came all over his fingers. He was vaguely aware of Sebastian thrusting up against him just a few more times before following him over the edge with a curse and by the time Alec found it in himself to step away, he seemed perfectly composed again.
He couldn't say the same about himself, Alec suspected, even if he tried not to let it show. He buttoned up his jeans with a grimace, the fog of lust in his mind giving way to a clarity he wasn't quite prepared to deal with right now. This was a bad idea. He refrained from saying so out loud, but it didn't make much of a difference – Sebastian could clearly feel his hesitation well enough because he neared him again, his eyes dark under the dim glow of the screens behind them. "There's just one camera in here," he said and while the words were perfectly clear, the same undercurrent Alec had noticed before was still there; the way the man's expression flickered between coy and his usual soft-spoken demeanour disorienting enough to throw him off for a moment. "And the feed goes straight to your office, if that's what worries you."
"There's nothing to be worried about." Except there was, and the enormity of it was just starting to settle as Alec schooled his expression into its usual neutral state. "Is there?"
"Of course not." The smile Sebastian sent his way seemed almost apprehensive. "Same time tomorrow night? I was thinking that maybe we should up the security at the lower levels, but I wanted to run it through you first."
"Yes," Alec nodded. It had been nothing too out of the ordinary, he told himself; interoffice relations of any kind weren't exactly a novel concept even for Shadowhunters. Him not being used to it didn't change anything. "You can send me the details after the morning training."
"Will do." Sebastian lingered by the door, then seemed to make up his mind and leant in for a last kiss, quick and fleeting. It hadn't been a spontaneous decision; Alec could tell that much by the caution in the gesture even as he stepped away. The raw intensity of just minutes ago was gone, replaced by the already familiar assessing of every little thing in his surroundings, quiet and careful. "See you tomorrow."
Alec had barely closed the door behind himself before he headed straight for his room. Sebastian's touch on his body felt all too real even now, the skin burning where his fingers had been and – despite his own reassurances that the man had done nothing to earn his distrust – Alec could still feel his eyes on his back even as he'd walked away.