A/N: This scene was originally inspired by one of the illustrations for the military AU doujin developed by pixiv artist ID 328608, specifically the album with the work ID 46833240.

Iwaizumi is really good at sparring.

Oikawa has always thought of sparring as his strong point. He's quick on his feet, fast to react to other's movements and good at predicting what they'll do; he can fall into rhythm with someone within a few minutes of a session, can match his movements to his opponent's, and after that it's hardly any effort at all to exploit their weaknesses. The problem with Iwaizumi isn't the breadth of his shoulders, or the solid weight of his arms, or the fact that even when they're practicing he holds his fists up and balanced like he means business. It's not even the way his eyes shine with focus, or the fact that shimmer of sweat against his skin draws Oikawa's mind sideways into other things they could be doing to produce that radiant body heat.

The problem with Iwaizumi is that he just keeps coming. Oikawa can usually knock his opponent off-guard at some point, take advantage of their hesitation and throw his weight into the space to take control, but Iwaizumi doesn't leave any gaps, doesn't offer up any vulnerabilities. He just advances slow and steady, pushes Oikawa back across the practice mats until he's well over half the distance to the wall.

Oikawa can see how this will turn out. If he keeps going he'll end up with his shoulders against the wall, Iwaizumi leaning in to demand he surrender to his loss. There's no clear line to victory that he can see himself, but he's hardly going to go quietly into a loss, and a risk is worth it if it gives him a chance.

When he moves it's all at once, not giving Iwaizumi any warning at all. Oikawa steps over in front of himself, twisting in an attempt to swing his leg up and kick at the inside of Iwaizumi's knee. If he makes contact he'll be able to jar the other's balance, maybe knock him onto his back, and if Oikawa can get the advantage of-

It's a futile train of thought. The motion leaves Oikawa off-balance himself, as he knew it would, and the element of surprise he was hoping for completely fails to materialize. He's still moving his leg when an arm hits across his chest, the impact so much that it blows Oikawa's breath out of him even before he starts to fall, before Iwaizumi steps out of the way to let him land flat on the practice mat.

For a minute Oikawa can't see straight. His whole body is numb with the impact, his breathing static in his chest as he tries to reestablish his usual rhythm. Then there's a weight at his hips, Iwaizumi shoving him down by simple expedient of straddling him, and when Oikawa blinks his vision back into focus the other is leaning into his line of sight.

"Give up," Iwaizumi says, clear and deliberate. Oikawa can see the sound rumbling in his throat, the words tensing under the high neck of his shirt. "You've lost."

Oikawa can feel the bruising pain of his fall starting to spread out into his shoulders, the relief of numbness giving way to an ache that will linger for the next few days. But Iwaizumi looks confident, worse, looks unimpressed, and willful stubbornness burns itself up into a flame under Oikawa's skin.

"Give up?" he repeats, making it sound like a giggle in his throat. "But Iwa-chan, the fun is just getting started." He can't move his legs with Iwaizumi sitting on him, doesn't want to risk trying to sit up, but when he lifts a hand Iwaizumi doesn't stop him, doesn't react until Oikawa's fingers push up against his thigh. Oikawa can feel the way Iwaizumi goes tense, then, can feel the impulse to action drawing taut in his legs and across his shoulders, and distraction is good, distraction gives him something to work with.

"Can't we have another round?" he drawls, letting the words go slow and suggestive on his tongue. It's easy to do, when he can see the shadow of Iwaizumi's lashes framing the dark of his eyes, when he can feel the heat of the other's skin clear through the heavy fabric of his pants. Oikawa's hand slides up higher, he pushes hard with his thumb against the inside line of Iwaizumi's leg; he can feel tension humming through the other's body, drawing closer and closer to the breaking point into something. He's ready to take advantage of anything, rejection or interest alike; either way, it's a moment of distraction, a moment of Iwaizumi letting his guard down, and that's better than where he's at now.

A hand slams down against the practice mat, so close to Oikawa's face he flinches instinctively away from it. Rejection, then, that's hardly unexpected, and he's just bracing himself for the shout of rage Iwaizumi is likely to throw at him when the other leans in. Oikawa tries to flinch back, tries to duck the headbutt he's expecting to result from this action, but there's nowhere for him to go.

Then the contact comes, and it's not rejection after all, it's a kiss, and Oikawa forgets how to breathe.

He's kissed people before. Boy, girls, it doesn't matter, Oikawa knows how to kiss and he knows how to take control, knows how to lead his partner to the conclusion he wants them to come to. None of his previous kisses have been like this. This is like kissing a storm, this is like throwing himself into a hurricane; Iwaizumi is pushing him against the ground from the force of his motion, catching Oikawa's lip between his teeth and biting so hard it burns pain through Oikawa's blood. He's leaning in close, his hips rocking forward so Oikawa's fingers really are indecently high against Iwaizumi's pants, but Oikawa can't even pay attention to that anymore. Any thought of gaining the upper hand is gone, shoved right out of his head by the fist Iwaizumi's fingers are making in his hair; any hope he had of maintaining control is pushed aside by the pressure of Iwaizumi's lips crushing his, until when the other slides his tongue along Oikawa's lips Oikawa opens his mouth obediently without thinking. Then Iwaizumi is licking against his tongue, pressing friction up against the roof of Oikawa's mouth, and Oikawa is starting to tremble, adrenaline mounting too high for him to maintain the steady hands he prides himself on.

By the time Iwaizumi pulls away, Oikawa has fully lost his grasp on the passage of time. His entire world has become Iwaizumi's mouth, all his focus melted into breathless teeth and tongues and lips, his body thrumming response until he has forgotten all about the ache in his shoulders. The motion of the other pushing up and away pushes Iwaizumi's hips against Oikawa's forgotten fingers, provides ample evidence of his interest flushed hard against the fabric, but any advantage to be gained by that is long since lost; Oikawa is so hard against Iwaizumi's thigh that the motion of the other sitting up is enough to make him whimper, enough to rock his hips up in unconscious attempt at stimulation before Iwaizumi leans back to pin him to the floor.

"Two-zero, my win," he says, and if he sounds breathless Oikawa is just impressed that he remembers how to speak. Iwaizumi stares at him for a moment, the dark in his eyes gone superheated and dangerous; then apparently satisfied with Oikawa's submission, he pushes up and away, turning his back and walking towards the door of the gym without saying anything else.

It's for the best he doesn't linger. Oikawa doesn't know what he would say, isn't sure how to put words to the desperate heat in his blood, the desire so strong it feels like an addiction he only just learned to see.

It's weird to see seduction from the other side.