It starts as a thing. Well, it's always a 'thing,' with them; there's the confined-spaces thing, the fasten-your-seatbelts-because-we're-flying-Air-Iron-Man-and-your-pants-won't-stay-on thing, the frankly unavoidable costume-fetish thing, the slightly less unavoidable (unless you've seen Steve's perfect feet, damn it, even his feet are perfect) foot-fetish thing, the Steve-doesn't-molest-his-food-because-his-food-molests-him thing, and… things. Lots of other things.
If Tony were more organized, he'd make a list, but Coulson makes enough lists for all of them, and the only list Tony's interested in making is one that can be tattooed onto Steve's ass, each item counting the number of times that fabulous behind has been a) reamed, b) rimmed, c) fucked, d) fingered or e) all of the above. Not necessarily in that order.
So, it's a thing. Steve heals really fast. Really, really fast. That means stretching him takes time, and maybe it never actually works, because the way Steve flinches and shakes every time makes Tony feel like he's taking a virgin, makes him slow down and whisper sweet nothings (okay, just filthy nothings), makes him stroke his hands down Steve's quivering flanks and tell him how good he is, how well he's taking it, he's such a lovely boy, such a good, good boy.
And Steve gnashes his teeth and glares at him, eyes wet and indignant, and that's what makes Tony give in, finally, what makes him laugh and love and fuck, just that bit harder, that bit deeper, until Steve opens up for him and curves upward like a plucked string and comes all over himself, and Jesus Christ, it's still the most religious experience in the world. Tony could worship at Steve's come-slick altar. (Oh, wait. He already does.)
Anyway. The thing. Steve gets impatient with all the prep, sometimes, tells Tony he can take it, that Tony's being pathetic, throws "old man" right back at him, sneers even as he tries, desperately, to catch his breath - but Tony won't hurt him, of course he won't, not unless Steve seriously wants him to, but what Tony doesn't count on is -
Steve wants him to.
Because one day, the Steve-heals-really-fast thing turns into another thing.
A thing that has Steve taunting him, saying that if Tony needs him that loose, maybe he should just shove his fist in there.
And in the ensuing silence, the shocked, echoing silence, they stare at each other, both disbelieving, and Steve blushes so hotly that his ears go red.
"Ignore that," he mutters. "Just - "
"No," says Tony, softly, and doesn't pull his fingers out. He curls them, instead, tenderly, and watches the muscles of Steve's thighs flex. "No, I don't think I will."
Steve eyes widen. And he looks away, swallowing nervously, and throws his arm over his face. It's enough to hide his expression, but not the flush spilling down to his chest.
"Let me see you," says Tony, but Steve doesn't move his arm.
"Just do it," he whispers, and spreads his legs, and he's -
Steve's hard, he's so fucking hard, and his dick's so stiff it doesn't look like it could be made of anything as vulnerable as human flesh.
Tony breathes through his nose and closes his eyes, because - because he has to do this right, has to give Steve what he wants, because that's their thing, the thing at the center of all their other things, and Tony can't just dry-hump the air and shoot all over Steve's dick because Steve's too fucking beautiful for Tony to last.
Instead, he just feels - with his fingers - the slick, oiled heat of Steve's ass, the unrelenting clench of it, hotter than the fires of hell, dripping lube past Tony's knuckles. They've already been at it for a while, and even with his eyes closed, Tony knows that Steve's skin has that sweat-sheened fever-bloom, that rose-tinged glow darkening to a bruised, bluish red at his bitten nipples and his swollen dick. Steve's hips are already moving in tiny, rutting circles, his chest hitching on broken inhalations of breath.
Just one more finger. One more, and that makes it four -
And Tony doesn't ease up. He works his thumb around the ridge of Steve's hole, talking to him, barely hearing himself over the roar of his own pulse. As if in a chemical dream, he opens his eyes just in time to see his other hand squeeze more lube onto Steve's ass, making it gleam like something gilded, something out of a god's wet dream.
He isn't going to fuck that ass, isn't going to think of himself, isn't going to think about anything but what Steve needs.
"Do it," Steve is rasping, his mouth the only thing that's visible because he's still hiding his face, damn it, "doitdoit, Tony, please."
Tony shudders. Who the fuck is he even kidding? This isn't for Steve, this is all for himself -
"P-please - "
"That's right," says Tony, mindlessly, and slips the edge of his thumb inside. The stretch is unbelievable, and he stares down at the sight, all five of his digits in Steve's ass, and it looks - it looks insane, it looks brutal, and Tony blinks away the sweat that drips past his eyes, feeling starved and nearly sick with it, his own body burning like a furnace. "That's good. Take it easy, you're doing fine, you're - "
"Do it!" Steve almost shrieks, and Tony -
Tony's hand is inside him.
Just like that.
The world freezes, for a moment, a tableau of agonized stillness, Steve's back arched and taut, his throat clicking mid-gasp, Tony's reality condensed to absolutely nothing but the clamp of Steve's hole around his wrist.
So hot inside, crushed velvet drenched in oil.
So tight, not giving way, not -
Tony pushes, and the tableau fractures, Steve's scream ripped from him and his limbs spasming like someone just electrocuted him.
"Does it hurt," Tony is saying, "does it hurt, you have to tell me - "
Steve's head just flops on the pillow, his arm dropping away from his face, his eyes rolling back -
"Steve. Steve, talk to me. Does it hurt - "
"Yes," Steve slurs, his eyes focusing again, because he heals just that fast, but it doesn't change how blown Steve's pupils are, how dark, like he's high on something. Like he's drugged. "Hurts, oh god, Tony - "
"Does it hurt good? Huh? How good is it? Tell me."
"G-good. Oh, f-fuck, good - "
"Am I making you feel it? Am I making you feel it, sweetheart? As deep as you want?"
Steve nods - hiccups - sobs, and his sounds are everything Tony needs, from the torn half-gasps coming from his mouth to the loud, splashy slaps coming from his ass, which Tony is fucking with his hand -
He needs more lube -
He gets it, spare hand almost fumbling with the tube, but then there is more lube, a lot more, soaking the fucking sheets between Steve's thighs, and the noises are filthier than ever, wetter than ever, if not as wet as the grunts falling out of Steve's mouth -
They're falling out, like Tony's fucking them out of Steve -
He is fucking them out of Steve -
And closes his hand into a fist. Carefully. Carefully.
Steve's dick spatters a string of pre-come onto his abs.
Tony can hear them breathing. Tony can hear them both breathing, but in Steve's case, it's more like choking.
Everything congeals, time and heat and thirst, never-ending thirst, because Tony's throat is so dry it hurts.
Not as much as Steve is hurting.
Never as much, and it still isn't enough.
And it's like suspended animation, the moment before Tony chooses to do this, chooses to do what Steve's wild, crazed eyes are begging him to do -
He thrusts. With his fist, with his entire -
And he tries to tell himself that it isn't a punch, that he isn't -
That he isn't breaking Steve, he isn't -
He is, oh, fuck, the way Steve keens -
Steve's hips jolt off the bed and Tony has to press them down with his free hand, has to keep Steve still, has to watch him shatter in slow increments, steady increments, hard increments -
Because that's how Tony is fucking him. Slow, steady, hard -
And each thrust makes Steve's dick jump a little, makes Steve's body judder like it's been hit, and it's -
It's too much like (battle) -
It's nothing like -
He bends Steve backwards, gets Steve's knees up around his shoulders, and shoves in deep. Steve goes quiet, the wail that's been building in his chest cutting right off, like he's been beheaded, like he's been -
Steve is gone -
He isn't even making any sounds, anymore, other than the raw, hoarse sawing of his breaths, in and out of him, and his eyes keep rolling back, keep focusing, keep rolling back -
He's slipping in and out of consciousness -
His dick is so hard -
Tony's lubed up to his forearm, and it disappears all the way into Steve, halfway to the elbow -
Again. Again -
Faster, even faster, so that Steve can't heal around it, can't tighten, can't do anything but let himself be fucked loose -
Oh, god, he's loose, he's fucking sloppy -
And Tony's saying things, horrible things, about what a sweet pussy that is, how he's going to fuck it until there's nothing left of it, how he'll wear Steve down to nothing but a nerve, a twitching nerve, a patch of sensitized, scalded skin -
Steve isn't responding, isn't even hearing him -
He's more unconscious than conscious, by now -
And then he's coming. Steve's coming, and Tony can feel it before it happens, feel it from the inside, the maddening, impossible spasm that wrecks its way across Steve like a goddamn tsunami, and what makes it worse (better) is that Steve's still silent, lips slack and trembling as he comes on his own face -
Because Tony's bent him back that much, forced him back -
He pulls out of Steve, as gently as he can afford (not gently enough) and lets Steve's legs fall back onto the bed. Steve still doesn't move - he's definitely blacked-out - but Tony can't wait, so he scrambles up to straddle Steve's shoulders and bury himself in that mouth, that soft, drooling, helpless mouth.
Warm, god, warm and gorgeous, the most gorgeous thing there is, and for some damn reason his own eyes are damp, and he can't think, can't -
He pulls away before he comes, jacks off onto Steve's flawless chest. His mind throbs, like an open wound. A pure, flaming white eats away at the edges of his vision - but he can't look away from Steve, not for a second, can't wait for Steve to wake up -
Steve doesn't wake up. He still hasn't woken up, after Tony's been sitting there, shaking, for a good few minutes.
Might as well get cleaned up.
Tony swings his legs - surprisingly unsteady - off the bed, and heads to the bathroom to wash his… hands.
His hand. His - his arm.
Fuck, there aren't -
There aren't any traces of blood, of course, this is Steve, but it's -
It's okay. It's okay. Steve wanted this. Steve needed -
Tony needed -
Tony pads back into the bedroom, gets JARVIS to dim the lights to 5 percent, and climbs back into bed with Steve.
It's a thing. It's one of their things, to kiss for ages after they're done, and so he's kissing Steve, when Steve wakes up, his fingers carding through Steve's sweat-sodden hair. He's sponged Steve down, which he's sure Steve will appreciate when he's aware enough to think, but for now, all Steve does is curl into him and sigh.
He's healed, obviously.
He's - he's healed.
And there's the fact, sitting between them, that Steve doesn't want to be healed.
"Wanna talk about it?" Tony asks, after a while, and Steve snorts one of his weird postcoital snorts, half-snuffle and half-cough.
Tony smoothes a hand down Steve's shoulder. Steve's relaxed, in a bone-deep, undeniable way, and Tony tries to remember the last time Steve was this relaxed, the last time he -
"Stop thinking," Steve murmurs, and throws a heavy leg across Tony's waist. Jesus. Michelangelo would've killed to sculpt a thigh like that. All power and lift and muscular weight.
It's exactly like sleeping with a sports car. A muscle car. And that's another thing, too, another thing they have to do, that, arguably, they've been doing, throughout -
"Sleep," Steve huffs, finally, and settles a moist palm over Tony's eyes.
Tony moves it down to his lips and kisses it, right over the massive shield-callus. "Shouldn't I be easing you down?"
"You're still shivering."
Is he? Oh, hell, he is.
"I think you might be in shock."
And there it is - that insufferable little smirk, that never stops looking out of place on Steve's lush, generous mouth, except that it also manages to look like it belongs there, always, like Tony needs to make it belong there. "Fuck you, Captain America. Not all of us have mutant healing powers. Some of us actually think this is a big deal - "
"Mm," mumbles Steve, and closes his eyes. "It is."
"Did you just - "
"Sleep," says Steve, right up against his ear, and, damn, wouldn't that make any guy shiver?
Tony can't sleep. No matter what Steve says.
But what he can do is hold on as Steve sleeps, slipping into a languorous mess of tousled hair and flushed, cooling skin, that fills Tony with the near-painful compulsion to draw him, like one of his blueprints, from the toes up, every angle and curve committed to memory.
Maybe he will, one day. It'll be a thing.