Based off this prompt from livejournal:

Chekov is alone on bridge. Naked, bound, and gagged.
What should Sulu do to him upon this discovery?
Well he certainly isn't going to untie him.

If Sulu couldn't see the way Chekov looked at him, Jim thought he must be blind. Seriously, everyone knew how the little Russian felt, but no one said anything for fear of offending him. And Sulu was just a blind idiot who was missing out on what Jim was sure was great sex with a horny teenager. So Jim decided to help Chekov.

"Hey, Chekov, wanna come to my quarters later for a drink?" Jim asked casually as they were all leaving the Bridge for dinner. Jim saw Sulu tense as he asked the question, and it took all Jim had not to grin widely. The small Russian smiled brightly.

"Yes, Keptain! Zat vould be fun!" Jim smiled.

"Great. Straight after dinner good?" Chekov nodded happily.

"Da! I have night shift tomorrow, yes? Not tonight?" he asked, making sure it was okay for him to be drinking.

"Yeah, you have tomorrow night. Now come on, I'm starved," Jim remarked, slinging an arm over Chekov's shoulders. It was a good thing he had informed Spock of his plan before hand, to avoid the wrath of the Vulcan when he was getting touchy-feeley with Chekov.

Jim let him get a few drinks in him before beginning to talk about the real reason they were alone together.

"Pavel, are you gay?" Jim asked, opting for bluntness over tact.

"Uh…yes, Keptain. Vhy?"

"I've seen the way you look at Sulu. Everyone has."

"Did he ask you to make me stop? Does he hate me?"

"Hikaru? Nah, he's the only one who hasn't noticed yet. Trust me kid, you're not exactly subtle."

"Und vhat should I do? Go up to him und shout zat I luff him? No, he tink I am stupid boy!" Pavel ranted, drinking from the bottle of Vodka he held between breaths.

"You don't have to say anything, Chekov. I can help you get him. I know he likes you, yes, yes he does," he persisted at the shake of Chekov's head.

"How you help?" Jim grinned deviously.

"Here's the plan…"

Pavel swallowed nervously. This was a stupid idea. Stupid, stupid, stupid! Why was he doing this? It wasn't like Hikaru liked him anyway! There was no reason for him to. There was nothing desirable about a scrawny little 17 year old kid. But it was too late now, there was nothing he could do to get out of it now. His hands were tied, rather literally.

Hikaru bit his lip again, still debating whether he would go down to the Bridge tonight or not. He had told the Captain he would go down to keep Pavel company, but now he wasn't so sure. But he had told the Captain, who had undoubtedly told Pavel, Pavel in the Captain's bed. No no no! Not like that, they were just drinking, something Sulu had done often enough with Scotty and Bones. But still, that kid, Jailbait, and Kirk wanting anything gorgeous enough, Pavel was gorgeous enough. Hikaru brooded as he shifted and paced around in the tiny turbolift to the Bridge, which didn't take as long as he desired. God he should have drank a little before coming, to hell with regs about being totally 100 percent sober. As soon as the turbolift doors opened, Hikaru stepped off into a seemingly empty Bridge. He glanced around, mentally cursing Kirk for making him take Pavel's shift, probably because they're fucking. And there's a noise, a muffled whimper and Hikaru looks around again, this time catching sight of the top of a curly head behind the console. There was no way they were…not even Kirk was that much of an exhibitionist. Hikaru walked around, almost afraid of what he'd see. What he did see was totally different than what he had expected…

Pavel was kneeling on the ground, completely naked, wrists tied behind him to his ankles and a gag in his mouth. The only thing giving him any actual coverage was a cardboard sign over his cock. Hikaru's first thought was to untie him, to find out what had happened. It didn't even register that he was painfully hard at the sight of the seventeen year old tied up, waiting. Pavel kept looking down at the sign, so Hikaru looked down too. There were two things on that sign, the word "don't" and an arrow to flip it over. He blushed, realizing that would mean taking it off Pavel's cock. Pavel who was, on second glance, bright red in embarrassment. Hikaru knelt down and took the cardboard, turning it over.

Don't untie him, Hikaru Sulu. And don't walk away. He doesn't get up 'till you've fucked him nice and hard. You know you want to, and you're an idiot not to see that he wants you to. So what are you waiting for? I'd say 'take a chance', but there isn't one at all…

JK

Hikaru looked back down at Pavel who was staring down hard at the floor.

"Pavel?" he asked softly. He didn't look up. "Pavel, is it true you want me?" At this he looked up, staring sadly at Hikaru. "Do you want me to take the gag out?" Pavel shook his head franticly, moving his head to look at another piece of black fabric on the floor, and closing his eyes hard to try and motion that he wanted to be blindfolded. Hikaru shook his head. "If you're just trying to get off 'cause you're horny, or if Jim is taping this, I'm not doing it." Pavel looked confused. Hikaru sighed and reached around, pulling the gag from between the boy's lips.

"Jim?"

"Yeah, aren't you two fucking?" Hikaru asked, a trace of bitterness entering his question at the end. Pavel shook his head slowly.

"Ze Keptain is mated vith Meester Spock," Pavel said, cocking his head. "Vas he wrong? Do you not like me?" Hikaru shook his head as he felt tears prick the backs of his eyelids. They did start to fall at the broken look on Pavel's face.

"No! Chekov- Pavel, I do like you, I do want you, and that's the problem! It's illegal, and I feel like a dirty old man, and I didn't even know you wanted me," Hikaru trailed off, looking directly at the bound Russian in front of him. He reached forward and pressed their lips together softly, moaning as Pavel deepened the kiss as much as he was able with limited mobility. "God Pavel, you have no idea how long I've wanted this," Hikaru muttered as they broke apart. Pavel smiled and leaned forwards, toppling onto Hikaru, arms still tied to his ankles.

"If we're going to do anything, even make out, you aren't going to be tied up," Hikaru said firmly, swiftly untying the ropes that bound him.

"Ze Keptain said you vould-" Pavel began.

"Anything Kirk told you about what I would like is irrelevant, because Kirk is a kinky bastard who can't read people," Hikaru interrupted, ghosting his lips over the delectable shoulder when he leaned back after untying Pavel. Pavel leaned forwards and pressed their lips together, snaking his arms around Hikaru's shoulders. Hikaru pulled back with a groan. "Pavel, we're on duty."

"Zen set ze alarms to go off loudly if zere is problem, and set ship to autopilot," he suggested, nipping at Hikaru's neck. Hikaru groaned and stood to do as instructed. He hobbled over to the console, flipping some switches and entering his password. He hobbled back over and collapsed next to Pavel, allowing himself to be pinned to the back of the console. Before he could blink he had a lapful of horny teenage Russian, with fumbling yet eager hands and an amazing talent for finding every spot on Hikaru's body that would make him squirm. Needless to say, it was the best sex either of them had ever had, despite Pavel's sharp elbows and Hikaru almost passing out from being tackled to the floor too hard.