Steve doesn't resent the Extremis, he really doesn't. How could he resent something that grew Tony a new, healthy heart; something that's helped Tony and himself and their friends out of danger so many times? It's not resentment, it's just... Sometimes he doesn't want to think about it. Specifically, about what it does to Tony, or what Tony lets it do to him, when he overuses it, and he works too hard for too long and Steve feels like he won't be able to pull him out of his own head when it really matters.
Not everyone notices it, the subtle changes in Tony over the periods of days or weeks where he's overworking himself, pushing his brain to its threshold, to the point where his attention is so scattered and fragmented that nothing can be afforded full concentration. Steve tries to give him breathing room when it happens, just moderating from afar so he'll be able to pull him out when it looks like he's forgotten the order of the hierarchy of human needs. And Steve would be able to live with this arrangement if it wasn't becoming increasingly more difficult for him to distinguish between Tony – the real Tony, the man who pulled him out of the ice and gave him a life and a friend and a home when Steve was lost, fifty years away from anything he'd ever known – and the computer code coursing through his brain. And there has to be a distinction.
But all Steve can do is watch – because the Extremis isn't going anywhere – and make sure he keeps Tony functioning on a level that's as close to normal as Tony Stark has ever been capable of.
It's obvious that he's used to it by now, Steve's watchful eye; he barely argues when Steve intervenes after three solid weeks of work and almost no sleep (that Steve has seen), and informs him he's taking the night off.
Tony is still wired when Steve marches him out of the shop and up to bed – whether from caffeine or adrenaline, Steve doesn't know. He leaves a lamp on, intending to read until he's quite sure Tony is asleep and therefore not going to sneak back downstairs the moment Steve closes his eyes.
But Tony has other plans. Kneeling on the edge of the bed, he's pawing at Steve's chest before Steve has even has a chance to sit down, grinning up at him and going for the waist of his pajama pants.
Steve catches the roaming hands before they've had a chance to strip him, holding them gently and keeping his expression as light as possible, smiling down at Tony. "Hey, you should sleep."
Tony's reaction time is still half a beat slower than it should be. Steve tries to chalk it up to sleep deprivation, but the more likely candidate is that there's a screen somewhere in the Tower that's scrolling with fresh code. Still, the grin doesn't falter, "Are you sure you don't mean, 'Hey, you should blow me?' Because that was more what I had in mind."
"Tony." Steve shuts his eyes. He hates looking at Tony's face when half his mind is in another room; the only thing worse would be looking down with Tony's lips around him and knowing he's only doing it out of obligation, wondering whether he's sharing Tony's mind with a computer in his office.
Sex can wait until Tony lets himself relax; right now Steve's pretty sure he's just trying to make up for his absence. "Let's just-" He nudges Tony back, pushing the bedclothes down and pulling Tony underneath with him. Tony lays his head on Steve's chest, but shows no sign of having abandoned his goal. Long, nimble fingers dance over his abdomen, tracing the waistband of his pants, and Steve's breath hitches at the contact. Tony's hands are perfect; his body can't deny that even when his mind wishes it could.
Tony makes a small noise of triumph at the reaction, turning to prop his chin on Steve's chest, smirking. "Still want to sleep?"
He keeps his tone careful and even, "You should sleep. You must be exhausted."
"Mmm," Tony's not really listening, he's grabbing Steve's crotch instead. Without thinking, Steve makes a noise of frustration, swatting his hand away, and regrets it immediately. Tony recoils, putting several inches of space between them and staring at Steve, expression somewhere between hurt and concern. "What-" But rather than have to explain why he'd suddenly become a complete jackass, Steve surges up and kisses him, shoving him onto his back and crushing him to the mattress. It's not worth denying him. Steve can improvise.
He kisses Tony deep and hard, grinding against him, not letting up until he's hearing throaty whimpers and Tony is clawing at the sheets. "Tony..." Tony answers with a moan, eyes distant and unfocused... That could mean anything. "Are you with me?"
He nods quickly, though it's obvious he doesn't know what Steve's really asking. He leans up for another kiss, but Steve pulls back after just a few seconds, hovering inches above him, watching intently, his face – his eyes, watching them flutter as Steve pushes his hand into Tony's boxer-briefs and grips his cock, stroking a few times, methodically.
"Ah, ah, ah," Tony's gasping, squeezing his eyes shut as his hips raise off the bed a little, pressing up into Steve's hand. But he doesn't linger, and Tony curses softly when the contact is lost, one hand tangling in Steve's hair. Steve tugs at his underwear and Tony wriggles out of them eagerly, licking his lips and smiling as he settles into the pillows again, rubbing his bare cock against the cotton covering Steve's hip. “Now can we do something about your pants?”
Steve doesn't answer, instead reaching for the nightstand, retrieving a tube of lube from the drawer. He pushes Tony's thighs open with his own and sits up, kneeling between them, the bedclothes falling from his back and leaving Tony exposed. Steve slicks two fingers, watching blue eyes slip closed again as he touches them to Tony's opening. No, that's not gonna fly.
"Look at me." He does, but his gaze is unsteady, and Steve can't see much of anything under the heavy lids and dark lashes. He leans over Tony again, planting a hand by his head and insisting, "Look at me." Hopefully without voicing the note of urgency he's feeling. Tony's eyes lock with his then, focusing, and Steve stares as he eases his fingers inside, stares as hard as he can as though he might be able to see the code flickering past if he looks deep enough into those blown pupils.
Tony's body tenses exquisitely at the intrusion, relaxes with a sigh, eyes fluttering as he fights not to break Steve's gaze. That's good, concentration is good. Steve slides his fingers out, crooking them a little as he goes, pushing them back in to make Tony arch his back, supplementing the contact that Steve knows isn't much more than a tease. Withdrawing again, he pauses, fingers just barely inside, and Tony trembles on the edge for a second before rolling his hips, forcing them back in. Still Steve doesn't move, and Tony picks it up fast; it generally doesn't take much encouragement to have him fucking himself.
Steve snakes his free hand up Tony's neck, cradling his chin, holding Tony's head steady as his body moves in smooth waves beneath him. Steve's thumb rests over his lips and Tony immediately opens, sucking it in, moaning rough and low in his throat, hips pushing down harder. Trembling arms stretch upwards and Tony grasps the headboard, using it as leverage to impale himself on Steve's hand.
His eyes stay open the whole time, though it's obviously not easy for him, and he can't be using the Extremis now, can he? Steve hates that he doesn't know, that he's gotten so used to it that he can't tell anymore. Frustrated, he releases Tony's jaw, reaching up and prying one hand from the headboard, interlacing their fingers, resting them on the pillow above Tony's head.
"I'm here, Tony." It sounds lame and ridiculous to his own ears, but Tony whimpers, nodding. "Are you here?"
Tony's brow creases and his movements dial down a little, but he doesn't stop. "I-" He shudders as he rolls his hips down, shakes his head and tries again, "I'm here, yes, I'm here... Steve..." He squeezes Steve's hand reassuringly, but he's obviously confused.
"Are you?" Steve clenches his jaw; it sounds so stupid to say it out loud, but what can he do? "Are the feeds off? Are you here?"
Understanding dawns visibly on Tony's face and he stills but for a few twitches, letting go of the headboard with his other hand and wrapping it around Steve's neck, clutching. "Yes. Yes, I'm..." He pulls Steve down, kissing him fiercely. Pulling away, he continues, practically speaking into Steve's mouth, "Yes, they're off, yes, they're always off when we do this. You always get all of me."
Feeling simultaneously relieved, and like the world's most unobservant asshole, Steve can't help his little huff of laughter. "I thought..." He pulls his fingers out of Tony's body, twisting them and shoving them back in hard, relishing in the sharp cry that he knows is all his. "... You were working so much; I didn't think you'd want to stop." Could stop.
"Fuck," Tony lets out part of a laugh, followed by a groan, starting to shift again, "I'd have to be... A goddamn robot-"
Steve cuts him off with a kiss, already content with what he knows. Tony's movements are jerky now, Steve meeting each one with a push of his fingers, and it's no surprise when Tony stiffens, something like a sob tearing from his throat, and Steve feels the warmth of his come spill between them. "Fuck, fuck, Steve..." He moans, gripping Steve's shoulder tightly as his hips snap, rubbing against Steve's stomach, still fucking himself, twitching with overstimulation but not slowing down until Steve withdraws his fingers completely.
Minutes pass in relative silence but for the satisfying evidence of Tony being thoroughly undone, squirming and heavy panting, while Steve is content, for the moment, to press his face into Tony's neck and grin somewhat embarrassingly. He thinks Tony might be falling asleep, when- "Hey." A hand tangles in his hair, tugging lightly. He lifts his head, raising his eyebrows in question at Tony's smirk and imploring eyes. "You know it's still absolutely necessary that you fuck me, right?"
Well. You'd have to be a robot to turn that down.