Fuck, it was good. Spock was long and hot and thick, and knowing him, every thrust was aimed precisely to spend the maximum amount of time sliding against Jim’s prostate. Not that Jim was complaining. From the beginning Spock had set an unexpectedly fast, unrelenting pace.
“God, Spock!” Jim moaned, panting. “Nev-never thought it would be like this. Thought you’d take your time, have every move planned out, make it last for hours. Never thought you’d be this…” Jim hesitated. “…open.”
“Would you rather I slowed down to meet your expectations?” Spock asked with a teasing glint in his eyes as he punctuated his point with a purposeful slowing of his hips.
Jim whined low in his throat. He’d spoken too soon. Spock was still as cool as a cucumber. It wasn’t fucking fair that Spock could still be so calm and collected when Jim was reduced to a writhing mess. His cock throbbed in need, desperately wanting to come. He slid his hand down to fist himself but Spock caught his wrist, pushing it away.
“Do not touch,” Spock all but growled at him.
Jim didn’t like the tone, and in retaliation, he clamped his muscles down hard around Spock’s cock almost imagining that he could feel the double ridges and would have laughed at the sudden stuttering of Spock’s hips if it hadn’t felt so fucking amazing. Jim surged up, capturing Spock’s mouth with his own, tugging and nipping harshly at Spock’s lips, not letting up even when he tasted blood.
Spock gave as good as he got, pushing Jim’s thighs up against his sides, spreading Jim even wider as he sank deeper yet before pulling out to return with an almost punishing thrust. Jim tried to arch his back against the sensation but found himself unable to in the position and gasped instead. Spock used the opportunity and took control of the kiss, his tongue sliding into Jim’s mouth, tasting, mapping, conquering. For a moment Jim thought about biting him, but Spock’s fingers suddenly found his nipples, tugging and twisting, and Jim shuddered forgetting all about it.
No, at the moment, Jim was doing his best to hold on for the ride, arms sliding across sweat slicked skin and as they fought for purchase around Spock as every roll of his hips threatened to force the little breath that Jim had from his lungs. His legs trembled, protesting the strain of their position, but Jim couldn’t care less as every brutal shove of Spock’s hips brought him that much closer to orgasm.
Spock thrust deep, freezing in place and dropped his head against Jim’s neck with a deep groan. For a moment Jim thought Spock was coming, and Jim groaned and squirmed. Fuck, he was so close, if he could just get Spock to move a little…
Jim’s eyes widened as he felt something odd happening in his ass. If he wasn’t mistaken the base of Spock’s cock was growing inside of him.
Jim took a deep breath and another, squeezing down hesitantly, causing his own cock to jump against his stomach and pulling a moan from Spock.
“Fuck, Spock. What is that?” Jim asked, feeling it swell more, pressing against his prostate in a way that shouldn’t have felt so good. He’d been with plenty of aliens in his time, and none of them had ever had dicks that changed shape once they reached full hardness—though there had been some that could move in the most amazing ways—and he’s pretty sure he’d remember if he’d heard about this when they went over Vulcan anatomy and reproduction in xenobiology.
“What is what?” Spock murmured in his ear.
“This thing in my ass!” Jim yelp the last word as Spock’s hips moved, shifting the bulge inside of him and setting his muscles spasming. “Shit, Spock. Don’t move,” Jim hissed through gritted teeth.
Spock raised his head and brush back Jim’s sweat slicked bangs and had an almost apologetic look to him. “When I asked if you were aware of Vulcan anatomy, you informed me that you were familiar with the operation.”
“I thought you meant the double ridges. Not whatever this is.” Jim fought to hold still, but couldn’t help squirming as it grew past the point of exquisite and crossed over to too much. Against his will his body clenched down hard around it, trying to get it out, and Jim desperately tried to relax as that caused more pain. Squeezing his eyes shut, close to panicking, he whimpered, “Spock, please. It’s too much. I can’t.”
Jim’s mind’s boggled as Spock’s hand wrapped around his flagging cock and stroked it back to full hardness, Jim’s brain unsure what to make of the mixed singles of pain and pleasure. “I am most sorry, Jim. I was mistaken to not clarify my point, and for it you suffer. I had assumed you had experience. The swelling at the base of my penis that you are feeling is my knot. It’s an evolutionary trait of my species similar to that of the canids of Earth.”
Jim had been called a bitch many times in his life, but this had to be the closest he’d ever come to it being true. Maybe he’d see the hilarity of it later. “It’s okay,” Jim said. “It’s okay,” he repeated again, unsure which of them he was trying to convince more. But he was surprised to note that the pain was gradually lessening as his attention wavered between his cock and ass. He forced his muscles to relax, and they protested, twinging at the command before finally doing so. The pain practically disappeared and Jim groaned as Spock’s fingers tightened around his cock.
“H-how big?” Jim panted. Actually it didn’t feel so bad now. It was pressed up tight against his prostate, stimulating it in ways that he’d never experienced before.
Spock looked down at him, pupils blown wide but didn’t answer. Instead he said, “I’m sorry, Jim.” Before Jim could ask why he was sorry, Spock’s hips rolled, trying to shove himself deeper. Make that did shove deeper.
Jim bucked against Spock, his eyes wide.
And grow larger.
“Nghhh,” Jim groaned unable to voice words. There was no way. He couldn’t.
Spock dropped his mouth to Jim’s neck, biting down hard enough to leave a mark and causing Jim to yelp.
Spock suddenly shuddered above him, and Jim felt an unexpected coolness inside of him. It shouldn’t have set him off, but Spock’s hand never stopped its motion on his cock, and that combined with the unrelenting pressure against his prostate and the knowledge that Spock was coming in him, the thought that he was breeding Jim like a bitch until his knot went down, pushed Jim over the edge.
Jim’s world whited out, shrinking until only he and Spock were in it, until all he could feel was Spock over him, in him, as his balls tried their damnedest to empty themselves all over Spock’s hand. Jim floated for a while, lost in the sensation, but was pulled back to reality as a sudden muscle spasm in his leg informed him that his body was not pleased by his current position.
Spock, must have sensed it because he shifted, helping Jim straightening it. All the while, he was acutely aware of the fullness of his ass. It didn’t hurt per say, but there was a dull ache that Jim knew he would be feeling for days. He couldn’t believe that Spock was still coming, couldn’t imagine what that felt like.
Jim focused on Spock’s face, thinking he’d been open before, but this, he was totally relaxed and blissed out.
“How long will you be like this?”
“The likely tie is anywhere from twenty minutes to an hour,” Spock replied.
That wasn’t so bad, Jim thought.
But Spock continued, “However, it isn’t unheard of for individuals to last for four to six hours.”
Jim’s eyes must have gone comically wide at that. It wasn’t possible for someone to come that much.
He didn’t realize he’d voiced his thought out loud until Spock answered.
“Unlike humans, Vulcans produce semen only when needed. Do not worry, Jim. There is no danger to you in this,” Spock placated, seeing the growing panic in Jim’s eyes.
“Spock, I’m already feeling it. There’s no way I can…”
Jim trailed off as Spock’s fingers wrapped around Jim’s cock again, and his head dropped to nip at one of Jim’s nipples.
“Do you think I would leave you as such? You are not expected to remain passive in this. There is still much I can do for you,” Spock stated as he teased Jim.
“Oh,” Jim breathed as his cock plumped, swelling with renewed interest. Maybe this wasn’t so bad after all.