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Strangely enough, his heat was triggered by sparring with Bucky. Thank the good Lord Himself that they were just messing around in private, and not out with everyone else. All the rest of their team were alphas and Steve was pretty sure Bucky would’ve beat them all down if any of them so much as sniffed in his direction.
He knew his new size took some getting used to, but Bucky was always pretty good at rolling with the punches. Once it sunk in that this was reality, not some fever dream, Bucky said his scent hadn’t changed. Somewhere under the serum and the title, he was still just Bucky’s Steve. The comfort in that had seemed to shock them both. After the shock, though, Bucky punched him in the shoulder and called him the same old little punk, and it was business as usual.
That barely lasted a week and a half.
Normally alphas pinned omegas down, bit them, and knotted them until they’d be leaking for days. Steve was almost beginning to think he and Buck were just hopeless on doing anything traditionally. That was alright, though.
Before everything Steve had asked, of fucking course he’d asked, if he would go into heat, if that was a risk factor. Erskine had shrugged and been brazen enough to tell him that everything was a risk factor. Only a doctor could dodge and answer a question at the same time.
It happened when Bucky’d tried to throw him, only to get tripped and immediately receive a full-body pin against the floor. Steve had hardly realized it was happening, what the line of fire from his ass to the nape of his neck meant. Bucky knew—eyes sinking into lusty black with his pupils wide and nostrils flaring—but Bucky’d been stuck under him on the floor.
For a long minute they just stared at each other, then finally, “am I?”
Bucky nodded, then glanced at the door. “Should I?”
A clock on the wall ticked on, one second, two, three, four. Steve shook his head and buried his face into Bucky’s neck. Maybe his senses were better now, maybe it was the heat, but Bucky smelled better than Steve could ever remember. Even back when his knot had first popped and all the milky sweetness of youth was replaced with something that made Steve’s lung fill with just a little more air than usual. This was better.
They both shook when Steve rolled his hips down. Bucky was half-hard and getting harder with every second. Steve inhaled as deeply as he could, sparks skittering across his skin, fanning out as sweat started beading up across his back.
Bucky at least had the good sense to try and push him off. “Not on the floor, c’mon.”
Steve pressed himself down harder, too lost in the want and the take, take him, take the knot to care about things like rug burn from fancy safe house floors.
Bucky shoved up more insistently, the edges of a rut coming on from Steve’s fresh heat. “Stevie, up, we’re not doing this on the floor, you horny little punk.”
Steve laughed and let Bucky get him to standing, but whatever plan they’d started concocting was lost as soon as they were vertical. They started tearing each other’s clothing off. First was Bucky’s shirt, then Steve’s, and then Steve’s pants were ripped as they tripped their way to the couch. Couldn’t even be bothered to make it all the way to one of the cots.
They laughed together as Steve kicked them off the rest of the way and pulled at Bucky’s belt. His hands were batted out of the way, Bucky quickly wiggling around until he was naked, too, save for his dog tags.
Skin-on-skin felt so good, better than Steve knew it could. He straddled Bucky’s thighs and felt himself start to drip for the thick cock sitting hard right alongside his own. Even now, after his procedure, he wasn’t quite as big as Buck, but that was fine, he wasn’t the one with a knot.
He reached down, only for Bucky to swat his hands out of the way again. A soft growl rattled at the back of his throat, and Bucky growled back.
"Gotta prep you," he said.
Steve shook his head. “No, gotta get you in me.”
He reached down again, but Bucky’s hand flew to the back of his neck, grabbing tight with his nails digging in, and Steve’s entire body froze. A shiver made Steve’s entire body tremble, sweat rolling down the curve of his spine and down his chest. Bucky smiled against his skin and licked a path from his sternum to his collarbone.
Two gentle fingers rubbed across his wet hole, relaxing him and making him sigh.
"I’m not gonna hurt you—"
"I know—"
“Steve.” There was an edge in Bucky’s voice that made Steve stop, a gasp hitching his chest his body easily opened enough for one finger to sink in to the second knuckle.
Bucky nosed at the hollow of his throat and slowly released the pressure on the back of his neck. Steve’s eyelids fluttered and he leaned forward, his forehead resting against Bucky’s
"What the hell was that?" He set his hands on Bucky’s shoulders and moaned softly when another finger slid in.
Bucky met his eyes with a lopsided grin. “Somethin’ mates do.”
Steve’s chest locked up and his stomach jumped, breath shaking as he exhaled slowly. “Oh.”
He really liked how that sounded.
"Let me prep you, then you can have it however you want it. Promise." Bucky nipped at his lower lip, two fingers pumping in and out in something pleasant, but definitely not enough. "You were always too sick for a heat, so this is overdue by about six years. I’m sure we’ll have time later to take things rough, if you want."
Steve nodded softly, brows furrowed as Bucky started to spread his fingers apart. “I thought omegas were supposed to just take it.”
Bucky still had the presence of mind to roll his eyes, even as he got three fingers in. “Do me a favor, let me punch whoever told you that when we get home.”
Steve laughed and could feel Bucky’s answering laugh right on his lips. They both seemed to realize at about the same time that they hadn’t even kissed yet, because they both went for it at the same time.
The slide of Bucky’s tongue over his made him clench, a fresh wave of heat rolling through him. He groaned and slid one hand down to finally grab Bucky’s dick, no interruptions or deflections this time. It jumped in his grip, Bucky gasping and biting his lower lip a little too hard.
He pulled back and looked down at Bucky, lips red and eyes more wide than when they first saw fireworks together as kids. This felt like some kind of explosion.
Steve stole a quick kiss and panted against Bucky’s lips. “C’mon, enough prep, let me have you.”
Bucky swallowed roughly and pulled his fingers free. “You always had me, Steve.”
Before a comment could be made, Bucky was sucking all three of his slick-soaked fingers into his mouth. Steve just watched, catching the pink dart of tongue as every single drop was savored with a heady moan. He pulled himself together enough to remember the thick alpha cock in his hand and the gaping emptiness in his ass.
Bucky pulled his fingers out of his mouth and smiled up at Steve, a warmth in his eyes that was different than what the heat was bringing out in them both. It was something older, something no heat could ever inspire on its own.
The thick swell of the head made Steve glad for Bucky’s insistence on prep. It stretched him more than those three fingers had, a slight burn making his breath stutter. He sank down slowly, each inch making him moan louder than the last. Bucky just held on, keeping true to the promise of letting Steve have it how he wanted.
When he was finally completely full he sat there a moment with his hands resting on Bucky’s chest. He could feel the hammering alpha heart under his palms and smiled before lifting one of Bucky’s hands to feel him in kind. If they’d ever tried anything like this when they were younger he’d have died, plain and simple. But now he could have this, could take what Bucky was telling him he’d always had.
He picked himself up and they both groaned at the slow drag, his body still so tight and clinging desperately. Bucky shifted, chasing the sensation with his stomach jumping and legs shaking. The first round wasn’t going to last very long at this rate. Like Bucky said, this was overdue by six years, no way in Hell they were going to be able to hold out. Savoring could come later.
Steve shoved back down a little too hard, and it was a good thing he healed so fast now or he might’ve been sore later. Bucky’s hands slipped in his sweat, groping his muscles and skin, trying to feel Steve’s body working as he twisted on the next roll of his hips.
As much as he wanted to go slow, the enjoy it, the heat was starting to be almost unbearable, practically screaming in his blood like a thick fever. He let his fingers dig into Bucky’s pecs and bit his lip at the hiss of nails scratching down his abdomen. The rhythm turned dirty quick, slick sounds filling the air along with their pheromones.
People outside could probably smell it, even if they weren’t hearing it, and that made something primal and a little vicious in Steve very happy. Bucky would smell like him, more than before, different than before.
Their skin smacked together, Bucky sending his hips up into every downward thrust. They held each other’s eyes, too wrapped up to think about looking anywhere else. An explosion felt like a good way to describe it, pressure building until it was just too damn much to be contained. Steve grunted when he felt Bucky’s knot starting to swell, tugging at the end of each thrust.
He leaned in and shoved his tongue into Bucky’s mouth, able to taste his own slick on his alpha’s tongue. Maybe later he could lay back and Bucky could eat him out, shove his tongue in deep and taste his fill until Steve came all over his own stomach. Then Bucky could lick that up, too.
The knot throbbed on a hard thrust, half-popped. Every muscle in Bucky’s body was starting to tense up, he took a quick breath and held it, so close to finishing.
Steve pressed a kiss to the corner of his mouth, breath ragged as he spoke. “Knot me, alpha.”
Bucky’s back arched off the back of the couch, his fingernails digging in deep, and his hips slamming up to meet Steve’s. He groaned hoarsely, eyes slipping shut for the first time as the knot finally popped and tied them together.
The head of Bucky’s cock had been nothing compared to the knot. It felt as big as a fist, just sitting so perfectly inside, holding him open so he could take everything Bucky was spilling into him.
With another slow grind Steve came across Bucky’s stomach, watery splashes of clear omega come that smelled almost sweet.
Each pulse came with a tight squeeze on the knot, and Bucky shook with each one, jaw grinding. “Fuck, Stevie, you squeeze me much harder, and I’m gonna pop.”
"Sorry." Steve smiled and took a deep breath, leaning forward to rest his head against Bucky’s.
They sat hunched on the couch for a few minutes, just breathing against each other as the first wave of Steve’s heat slowly subsided. The angle would get really old really fast, but neither of them were eager to move just yet.
Steve felt something biting into the skin of his palm and realized he’d grabbed into Bucky’s tags without knowing. He let them go, a little bent but thankfully not completely mangled. If he’d destroyed a pair of Bucky’s tags and someone found out, which they would, he’d never hear the end of it.
Bucky rubbed slow circles into his back with one hand, the other reaching down and swiping up a bit of his come to taste. Steve moaned softly, a breathy sound that made the knot throb inside him. He squeezed it experimentally, pleased with the way Bucky growled, eyes sharp.
"So, uh, how long…" He let the sentence trail off. Bucky would know what he was asking.
Bucky shrugged. “Dunno. Never actually knotted someone before.”
Steve made a curious noise. “I thought you’d had sex.”
The flush on Bucky’s skin grew a bit darker. “Regular sex is different than knotting, Steve. God, didn’t you learn anything in any of those books of yours?”
Steve laughed and rolled his eyes. There wasn’t a book out there that ever would have prepared him for this, but that was just fine. He was more than happy to learn through experience.