Steve's not sure when or how it happens.
He thinks his apology following the defeat of Loki's invading force might have been where it started because when he'd pulled Tony aside while the others ordered their shawarma and said, “Stark, I'm sorry,” Tony had gone still, staring at him like he'd suddenly started speaking German. Steve had barreled on anyway, trying to look him in the eye and mostly failing because he'd felt like a complete idiot, and a jerk to boot. “My intel was all wrong and I said a lot of things about you that were just—dead wrong. It's been...rough, adjusting to this whole—modern world and I should have realized Fury wasn't telling me everything about you guys after the way we met and, geez, I'm really making a mess out of this. I'm not trying to make excuses,” he finally said. “I just wanted you to know that the things I said were said in ignorance and I'm sorry.”
For another few seconds Tony had kept right on staring, his mouth hanging open and Steve had swallowed before prompting, “Uh, Tony? Are you—”
“You're apologizing?” he'd burst, incredulous.
Steve's brow had furrowed. “Uh. Yes. I crossed a line and—”
“Okay, you know what,” Tony had said, holding up a hand. “I can't deal with this right now. I almost died, what, like, twenty minutes ago? And now you're apologizing to me and I can literally count on one hand the number of people who have ever offered me a genuine apology, so unless you've suddenly become the kind of guy who plays mind games—”
Steve had frowned. “It's not a mind game. I really am sorry. I shouldn't have said—”
“Yeah, okay, thank you, that's great, stop, stop, stop,” Tony had said and flapped his hand dismissively, before turning and moving to help Natasha with the drinks. “We're good,” he called. And Tony had clearly not wanted to talk about it, so Steve had taken him at his word and let it go. Now he thinks that maybe that had been a bigger deal than he'd realized. Since then he's learned enough to get the impression that Tony's remark about being able to count the people who'd ever apologized to him on one hand hadn't been an exaggeration. And Steve's found that idea pretty distressing.
Since then, Steve's felt Tony's gaze on him whenever they're in a room together. Tony's shameless about it, grinning cheekily whenever he bothers to acknowledge that Steve's caught him looking, his expression intent and thoughtful to the point that Steve feels like he can practically see the gears grinding away in Tony's head. He's not sure exactly what it is Tony's looking for and it makes him nervous, so after awhile he just starts to ignore it.
And that works great, until Tony starts looking in a whole different way.
Steve knows exactly when he first noticed that change because the first time it happens is in a debriefing after a mission where he'd gone against orders to drag Tony back from behind enemy lines.
Tony always shows up five minutes after everyone else, having to get out of the suit before he can join them, and this time, when he walks through the door, his eyes find Steve and drop to half-mast, a slow grin curling the corners of his mouth.
Steve swallows and shrinks down in his chair a little, feels the heat of a flush race up his neck into his cheeks and ears. “Tony?” he starts to say, bewildered, but Fury cuts him off, gesturing peevishly at a chair.
“Thank you, for joining us, Mister Stark. Have a seat.”
Tony doesn't pull his eyes away immediately and the blush in Steve's cheeks burns hotter. He squirms, hunches his shoulders, tries everything to make Tony stop looking at him like that and finally, after what feels like an eternity, Tony drags his gaze away, but not without smirking as he saunters over and drops into the chair Fury is standing glowering over.
Steve stares at a spot exactly two inches from the edge of the table for the first ten minutes of Fury's dressing-down, only letting his eyes dart up when he's asked a question directly because he doesn't want to see the looks on the others' faces and he's absolutely petrified to find out what Tony's might look like.
And it's not without reason, because just before Fury dismisses them, he actually relaxes enough to look up and glance around the table and all of his worst fears are confirmed when he gets to Tony and finds him still eyeing Steve with that half-lidded expression that makes Steve blush all the way to the roots of his hair.
Steve recognizes that look, he just doesn't understand why Tony's directing it at him. And why now.
When they're finally allowed to leave, Steve stays rooted to the seat, catching Clint's arm in his hand as the others trickle out. “Clint, ah, can I—can I ask you a question?”
“See you later, Rogers,” Tony calls and Steve closes his eyes for a second, trying and failing to fight back the rush of heat across his cheekbones.
“Sure, what's up?” Clint asks, leaning over the arm of his chair to listen.
Steve shrugs a little and twists his fingers together, tilts his head to the side. “Uh, I was just wondering if you, if you noticed... Um.”
“The way Stark spent the entire meeting looking at you like he was going to devour you whole?” Clint asks, blithe and Steve groans, covers his face with his hands. “Yep. I saw it. Totally threw off Fury's groove. You weren't helping.”
“I didn't even do anything!” Steve exclaims. “What the hell am I supposed to do?”
Clint shrugs. “You're an adult. That's up to you.”
That's pretty much the worst advice Steve has ever gotten.
Steve doesn't see Tony again for nearly a week. Mostly because he's busy as hell, but there are a couple of times when he guiltily slips away before he has to talk to Tony. Unfortunately, that all comes crashing down when the Avengers are ordered to go to a charity gala and Tony comes down to ride to the ground floor with him since they're the only two leaving from the Tower.
Steve's nervous right up until the elevator door opens while he's fumbling to get his bow tie done and then Tony's standing there looking at him like that again and Steve's alarm klaxons start going off. He feels like a cornered mouse and Tony's flashing his canines. Steve drops his tie.
Tony's eyes follow it, amusement pushing back the Other Look for a minute and Steve swallows. “Tony. Ah, hi.”
Tony smirks and stoops to pick up the tie, holding it out to Steve between his index and middle fingers, his other hand still casually stuffed in a pocket.
Steve reaches for it and Tony flicks it back, out of reach. “You've been avoiding me, Rogers,” he says, pinning him with a look.
“What?” Steve says, crossing his arms tight over his chest and shrugging, both shoulders nearly brushing his ears. “No, I haven't,” he protests, but it sounds weak even to him; he's panicking. The last time someone looked at him like Tony's looking at him now— Steve swallows down that thought, sweat breaking out across his forehead, under his arms.
That look is full of intent and coming from a guy like Tony—
“Look, Rogers,” he says, and for a second, the predatory look drops away and it's just Tony again, exasperated and maybe a little frustrated. “I've seen the way you look at me, okay? I know in the forties they weren't all open-minded or whatever, but this isn't the forties and I figured if you needed a little more of an obvious go sign then sure, I could do that. But I don't get this—whatever you're doing right now. So what's the deal? Do you want me or what?”
Steve freezes because, sure, he gets that Tony's an attractive guy—Steve's best friend looked a lot like Tony, tall, dark-haired, square-jawed and he always had a dame on his arm, the same way Tony seems to. So even if he did, there's no way Tony... Unless.
Tony must see something in his face because his mouth curls at the corners and his eyes start to glitter. Steve gulps. “I see,” Tony leers and steps forward into Steve's personal space, reaching up to loop the tie around the back of Steve's neck. Steve's breath gets caught somewhere in his chest as Tony works it around the collar of his shirt, making sure the lengths are even, his eyelashes long and dark against his cheeks.
Then he looks up and it feels like all the breath Steve's barely holding on to has been socked right out of him. “I'm going to kiss you now,” he says.
Steve squeaks out something that he thinks was supposed to be a word, hands springing up defensively, but Tony just wraps a hot hand around the back of Steve's neck and drags him down, presses their mouths together.
It's like the kiss from the dame at the base and nothing at all like it at the same time.
Steve still doesn't know what to do with his hands and they reflexively anchor at Tony's hip and at the curve of his ribs—Steve's not sure if he's trying to pull him closer or push him away.
Tony's lips are insistent, but soft; the feel of Tony's goatee and the bristly hairs brushing across his upper lip and along his chin, that's...something. He likes it more than he expected, likes knowing that it's Tony and the man himself makes a delighted sort of noise that vibrates against Steve's mouth when he presses forward and Steve likes that a lot.
Tony pulls back from him enough to breathe, mystified, “So you are into this,” and Steve likes the sound of that so much he takes Tony's face between his hands and pulls him into another kiss. Tony responds enthusiastically and it's great, really great until Tony's mouth opens slightly and his tongue glides across Steve's lips.
Steve recoils and presses Tony back, his heart suddenly pounding against the wall of his chest, his ears burning. Tony looks startled and he holds his hands up, looks at Steve like he's dealing with a wild animal. “Oh. Okay, Frenching is—we're not at that point, okay. That's fine. Sorry. Didn't mean to jump the gun.”
It takes Steve a second to place the word, to remember Bucky explaining to him in a low, excited murmur when they were kids and how strange and vulgar the whole thing sounded—then he tests that against the tingle still lingering on his lips, the slow roll of his stomach he'd felt all the way to his toes, in the roots of his hair. “No,” he says finally. “You just uh. You just startled me.” Then he adds, more uncertain, “Um. I've never...so if you could?”
Tony blinks at him and there's a sort of joy breaking on his face, like Christmas has come early. “Oh, go slow, sure, absolutely, whatever you need, big guy, just follow my lead—”
Steve gives him a look. “Just kiss me, will you?”
“Happily,” Tony mutters and then steps forward and takes Steve's head between his hands, hooks his thumbs underneath Steve's ears so he can brush the callused pads over Steve's cheekbones. Steve can feel the anticipation and anxiety thrumming just under his skin and when Tony opens his mouth, Steve's heart leaps into his throat. He pinches his eyes tighter shut, waits for the tingle that crashes through him when the tip of Tony's tongue slides against where his lips meet and then awkwardly eases them apart.
He half expects Tony to just—stick his tongue in, but that's not what happens at all. Tony brushes the point of his tongue very softly against the sensitive corners of Steve's mouth and the sensation is so startling that Steve's breath catches. It sends chills crawling up the back of his neck and then Tony licks Steve's lower lip from one side to the other and Steve clenches his hands around Tony's arms. His own tongue lurches forward and Tony's rises to meet it, darting along the side. Steve breathes out sharply through his nose and joins in in earnest, mimicking what Tony's done and earning an appreciative groan.
It's Tony who finally forces him back, panting, “Okay, Christ, a guy with diminished lung capacity and a guy with enhanced lung capacity do not go together, shit, Rogers, you learn fast.”
Steve's impressed he can still talk so much and so fast when he can barely catch his breath. His mouth is red and wet and it really makes Steve want to be kissing him again.
“So we're doing this,” Tony says after another second of silence. “We're gonna try the whole. The whole shebang.”
“Going steady,” Steve suggests, trying to smother the amused curve of his mouth. “I'd like that, yes.”
Tony nods and keeps on nodding. “Right,” he says. “Okay.” He lets out a slightly hysterical little laugh and then smothers it with a hand.
Steve smiles and leans down, gently tugging Tony's hand away to press a kiss to the corner of his mouth. He looks surprised, following Steve's face back up with his eyes.
“Yeah, okay,” he murmurs and then his eyes move to give Steve a once over, catching on the tie still draped around his neck. He reaches for it and Steve tilts his chin up to give him room to work. “I'm, ah, new at...monogamy,” he says, focused very intently on the tie.
“So we're both trying something new,” Steve says and Tony's eyes dart up, a little half-smile tugging at the corner of his mouth.
“Yeah, I guess we are,” he murmurs.
Steve smiles and kisses him again, just because he can.