Summary: Natasha and Steve train together. It's an interesting dynamic, both of them being relatively evenly matched. Both work to get the upper hand, but it proves difficult when all they want to do is give in and make out. Raising the stakes seems like a good idea, but then Tony walks in.

Natasha doesn't sleep well. That's a given. Obvious, makes sense, we get it. And it's fine, you know, she doesn't mind. She quite likes night time, actually. But she never usually expects anyone else to be up.
So, it is for that reason that when she gets a text from a certain someone at five am that morning, Natasha is rather surprised.

Curious but weary, Natasha reaches for her phone on the dresser next to the bed and turns it on. The screen flashes, showing her the lock screen on which sits a photo that she had taken with Steve in Vienna a few months ago. His arms wrapped around her head, smothering her in kisses while she mock protests, but secretly loves it. She smiles at the photo, before focusing in on the notification.

It's a text from Steve.

Training? I'm down on level 4 if you want to meet me.

She smiles gleefully and immediately gets out of bed. Finally, something to do.

She spars with Steve quite often, but not usually this early in the morning. Normally in group training sessions, as they are both more inclined in hand to hand rather than weight lifting or track exercise.

After changing into a black tank top and matching leggings, she grabs a pair of trainers and her duffle bag full of equipment and heads down to the gym and training area located on the fourth floor.

The lights are on when she arrives, casting a natural glow over the large open space. Natasha's feet slap across the thick gym mats covering the floor as she walks to the center of the room, where Steve is.

Steve wears a white tank top and black pants similar to Natasha's, and he is already sweating

He is busy with a punching bag, and so doesn't notice her enter until she has appeared right by him, duffle bag over her shoulder and a mischievous glint in her eye.

When he finally catches sight of Natasha standing next to him, he jumps a mile into the air, stumbling backwards on the gym floor in shock. She doesn't know why he was so surprised, she hadn't exactly been trying to be quiet, but oh well. It's fun.

While Steve catches his breath back and holds a hand against his heart to slow the rate back down, Natasha throws her bag aside with her shoes, all while laughing at Steve.

Then she heads back to the center of the room, swinging her arms and jumping on the spot to warm up a little.

"So, what you wanna do?" she asks Steve, who seems to have calmed down now and is standing facing her.

"I don't know, what can you do?" he starts teasing her, mood changed drastically, raising an eyebrow.

"Oh, so that's how you wanna play it, is it?" Natasha riles back, stretching her arm using her other. "Well, if that's what you want, then maybe we should start with wrestling."

Steve raises another eyebrow, but doesn't say anything.

Then Natasha pounces. She aims a punch to Steve's stomach, but he just manages to block it, even taken by surprise. He stumbles backwards as Natasha advances, aiming blows at his chest and midriff.

"Oh, okay then! You're just gonna beat me up, is that how it is?" Steve shouts over the sound of Natasha's hands meeting his fist.

Natasha laughs and then sweeps her foot around and knocks Steve's legs out from under him. He falls onto the ground and Natasha pins him down with a foot, hands on her hips.

"Sounds like a plan, soldier."

Steve struggles against Natasha's foot and she lets him up, both of them squaring up against each other again.

"So I won round one, right? That seemed like a pretty solid win." Natasha grins.

"Oh, in your dreams, Widow." Steve growls back, before diving at her in attack again.

He starts by wrapping two arms around Natasha's waist, then lifts her up over his shoulder, but she spins there, wrapping her thighs around his neck in her signature move. She holds his head tight there between her thighs while Steve stumbles around underneath, trying to dislodge Natasha from his shoulders. He reaches up and manages to grab a shoulder, pulling it forwards until his other hand meets her other shoulder, and then he slings her over his head and onto the ground with a smack, holding her there. Natasha seems unfazed by the impact, still struggling to get up from under him, but he straddles her to pin down her hips, and she is lost.

"You forget, you're not the only one trained in hand to hand, Romanoff." Steve chides. "I know all your tricks."

"Oh, you do, do you?" she says dubiously. Then she reaches up a hand and pushes Steve's right shoulder hard, using the leverage to lift her hips from under his and turn her body, tipping the scales so that Steve ends up falling onto his back lying on the mat under her, instead of the other way round.

"Well, you obviously didn't expect that one, did you?" she says triumphantly, leaning down to his face below her. Her face is so close to his, but she holds it there, teasing. After a few tantalizing seconds, she kisses him on the lips, quick and sweet, and jumps back up off him to her feet.

Steve gets up after her, his cheeks a little pink from the encounter, and they both stand for a minute, catching their breath and cracking bones, stretching out again. Bless Steve's little innocent heart.

"You're sweating." Natasha observes as she straightens up from her bent over position catching her breath.

"So are you." Steve points out, and he's right.

The short spar has left both with a thin sheen of sweat on their faces, tinting their pale skin a slight pink, rosy cheeks matching with Natasha's unkempt red hair.

"How about we step it up a notch?" Natasha challenges and Steve looks at her appraisingly.

"You sure?"

"Yeah. It's an even fight, time to throw some stakes in. Tip the scales." Natasha explains, moving over to her duffle bag.

"Oh, so like, 'if I don't win, I'll get-'" Steve says sarcastically as he watches Natasha fetch something from her bag. It glints silver in the harsh light, the blade short but sharp.

"- a knife in my throat?!" Steve says incredulously, staring at the knife Natasha spins in her hand.

"What are you, scared?" she grins evilly, fetching another knife from her bag and throwing them up in the air before catching them again.

"Oh, you are so on." he grins just as evilly back, breaking into a low crouch, ready to take her on.

There is a moment, and then they both simultaneously attack. Steve blocks a jab at his side from Natasha and grasps her wrist, twisting it and the knife up and away. Natasha aims a kick at his midriff, which hits, and sends him rolling backwards, leaving Natasha to free her wrist. He jumps back, feigning left only to dart right, spins around her and knocks her knees out, but Natasha only flips in the air instead of falling, and lands back on her own two feet, running and jumping at Steve and launching herself up over him with a foot on his thigh. The fight is really on.

She wraps herself around his shoulders again, one leg still holding herself up on his thigh. Steve struggles, grabbing for Natasha as she tries to jab at him with knives in her hands. They grapple, grunting as Steve tries to throw Natasha off him, but she holds on tight. She really is like a little spider. She earned her name.

Steve shouts in frustration as he catches Natasha's wrist but she frees herself again, determined to beat her. Here he is, first and only super soldier and none another than Captain America in the flesh, and being equally matched and even beaten by a Russian assassin with no enhancements or superpowers except her inhuman speed, skill and agility. He hates it, but he loves it.

He lets out a strange kind of laugh and switches, instead reaching up and jabbing Natasha in the ribs where he knows she is most sensitive. Natasha jerks at the movement and as Steve continues to tickle her, she starts uncontrollably laughing, gasping for him to stop as she clutches onto Steve for dear life to stop from falling off him. He holds her fast, making sure she doesn't fall, while she desperately tries to catch her breath through the laughing. When he stops tickling her and she gets control over her movements again, she wraps an arm around his neck and brings her knife to his throat threateningly. Steve freezes.

"Cheater." she murmurs, and then kisses him on his cheek and jumps down from his shoulders.

"I could say the same about you, dear." Steve smiles wanly back. He still hasn't forgotten that kiss.

The two continue to spar for the next hour at least, both equally balanced in skill despite the obvious differences between them.

When the sun eventually rises and they begin to tire out, they slow down their fighting, often stopping half way through to just catch their breath.

At one point, Natasha is on top of Steve's shoulders again, grappling with the knives. He has both her wrists in his fists and she is relatively beaten, but she still kicks him with her free leg diligently.

Then Tony comes in. He casts an appraising glance at the two Avengers, Natasha wrapped around Steve and him with his hands on her, stopping her. They freeze as he passes, holding a drink and walking over to the boxing ring, taking a seat on the edge facing them.

At their frozen bodies and shocked faces, he speaks up, "Oh, don't mind me, carry on. You seemed to be having a lot of fun." Then he winks and takes a sip of his drink.

That morning turned out to be the catalyst of many early morning training sessions that the two spent together as time passed, a way to maintain physical form and also spend time together. It was in it for themselves and they loved it.

And through the eyes of the other Avengers as they watched, they got to see Steve and Natasha grow as people and grow into each other, melding slowly until they seemed to share a brain, a heart and even a soul. They knew each other deeply, and intimately. And even when Natasha accidentally scraped him with a knife one session, they always came back and tried again. Because they always came back to each other.

A/N: I wanted to make a shoutout to @LCorbett04 for voting on every chapter of this book and supporting it every step of the way.