Chapter 1 — Sparks in the Training Room

Third Person

The sound of fists striking padded targets echoed through the Avengers Tower training room, punctuated by the rhythmic hum of holographic timers and the low mechanical buzz of nearby training equipment. Bright fluorescents gleamed off the polished floors, casting sharp shadows of the two figures locked in a heated sparring session. Nellie’s breathing was steady but quick, her movements sharp and calculated as she ducked a high kick from Bucky. She retaliated with a spinning elbow aimed at his ribs, but his vibranium arm absorbed the blow effortlessly, a metallic wall against her strikes.

"Too predictable," Bucky muttered, his tone flat and unbothered, though a faint smirk tugged at the corner of his lips—a smirk that set Nellie’s nerves alight with frustration.

"Predictable, huh?" she shot back, her voice sharp and biting. Adjusting her stance, she feinted left, darted forward, and landed a solid jab to his abdomen, her knuckles connecting with satisfying force. "Didn’t see that coming, did you, Tin Man?"

Bucky grunted, his expression unchanged except for the faint narrowing of his piercing blue eyes. He stepped forward with deliberate precision, forcing her onto the defensive. "You’re telegraphing. Makes it easy."

"Oh, because you’re so perfect?" Nellie scoffed, pivoting out of his reach. She cut a quick arc with her foot aimed at his knee, but he caught her ankle mid-strike with unnerving ease, holding her off-balance for a moment before unceremoniously dropping her back to the mat.

"Not perfect," he said evenly, stepping back. "Just better."

Rolling to her feet with fluidity, Nellie flipped her mussed auburn hair out of her face, her green eyes flashing with determination. She wiped a bead of sweat from her brow and gave him a crooked grin that was equal parts challenge and mockery. "Better? You sure about that, Barnes? Because from where I’m standing, you look one bad decision away from a face full of mat."

Bucky’s expression didn’t shift—stoic as always—but there was a flicker of amusement in his gaze, so brief it was almost imperceptible. "You talk a lot for someone who keeps losing."

"Losing?" Nellie let out a bold, sarcastic laugh, her voice echoing through the room. She began pacing in a slow circle around him, like a predator sizing up its prey. "You wish. I’m just lulling you into a false sense of security. It’s called strategy, Mr. By-the-Book."

"Sure, it is," he deadpanned, but there was a faint twitch at the corner of his mouth, almost an acknowledgment. Almost. That flicker of recognition—of her skill, her tenacity—was enough to keep Nellie pushing forward.

For the next few minutes, their sparring intensified. The air was filled with the sharp cadence of footfalls and the heavy impact of fists meeting forearms and padded targets. Their movements were a blur of precision and power, a stark contrast in styles—Nellie’s strikes were fast, unpredictable, and laced with reckless energy, while Bucky’s were measured, efficient, and unyielding. The clash of their approaches created a rhythm that neither could fully dominate, though neither would ever admit it.

“Not bad,” Nellie muttered between strikes, her tone light but edged with defiance. “For someone who looks like he should be standing guard outside a museum.”

“You’re resourceful,” Bucky admitted flatly, countering her jab with a quick hook that forced her to duck. “But reckless.”

"Reckless gets results," she shot back, twisting mid-dodge and using her momentum to attempt a sweeping kick. “Maybe you should try it sometime, Tin Man.”

But then it happened—a moment of chaos amid the precision. Nellie miscalculated a strike just as Bucky lunged forward, their momentum colliding in a tangle of limbs. She tripped over his foot, and before she could right herself, his vibranium arm shot out instinctively, catching her and pulling her weight forward. They tumbled to the mat in a heap, her breath punching out of her lungs as she landed awkwardly on top of him.

For a moment, there was nothing but silence, a tense pause hanging thick in the air like the stillness before a storm. Nellie’s heart thudded in her chest as her palms pressed against the solid plane of his chest. She became acutely aware of the faint hitch in his usually steady breathing. His blue eyes, sharp and guarded, met hers in a rare moment of unspoken vulnerability, and for a fleeting second, neither moved.

Nellie’s mind scrambled for something—anything—to break the tension. "Well, this is cozy," she muttered, her tone light but with an edge of forced nonchalance. Her lips quirked into a smirk as she pushed herself up, hands braced against his chest for leverage. "Didn’t know you were such a hugger, Barnes."

Bucky’s brows furrowed, discomfort flashing across his face as he sat up, brushing imaginary dust from his black training shirt. "You tripped."

"And you’re welcome for giving you the privilege of breaking my fall." Nellie smirked again, rising to her feet and extending a hand to him. Her gesture was more mocking than kind, her grin wide enough to make it clear she didn’t expect him to take it.

He didn’t. Instead, he got to his feet on his own, his jaw tightening just enough for her to notice. "You’re reckless."

"Reckless?" Nellie threw her arms wide, the towel slung over her shoulder swaying with the motion. "It’s called improvising. You ought to try it sometime, Mr. By-the-Book."

Before Bucky could respond, a slow, deliberate clap interrupted them. Both turned their heads toward the observation deck to see Tony Stark leaning casually against the glass railing, his smirk as insufferable as ever.

“Bravo, you two,” Tony called out, his voice dripping with mock enthusiasm. “Really top-tier teamwork. If the Avengers ever need a comedy duo, I know exactly who to call.”

Nellie rolled her eyes and snatched her towel from the bench. "Don’t you have a lab to blow up or something, Stark?" she snapped, swiping at her sweat-dampened brow.

Tony ignored her jab, wiggling his eyebrows suggestively as he descended the stairs to join them on the training floor. "I’m just saying, the sparks flying down here? Electric. Maybe less punching, more... collaborating."

"Not helping," Bucky muttered, grabbing his water bottle and taking a long drink. His tone was flat, but his knuckles tightened ever so slightly around the bottle’s neck.

"Oh, I’m always helping," Tony said breezily, clapping his hands together. "Why else would I spend my precious time observing your little therapy sessions?"

"Therapy?" Nellie echoed, her voice rising in indignation. "This is training."

"Right," Tony agreed easily, the corner of his mouth twitching upward. "Training to tolerate each other, maybe. I mean, the banter’s solid. Very Mr. and Mrs. Smith. But you might wanna dial it down before the mission. Hydra doesn’t appreciate slapstick."

Bucky’s glare was sharp enough to cut through steel, but Tony, as always, was unfazed. He strolled to the edge of the mats, hands in his pockets, and tilted his head slightly, as if assessing them. "Anyway," he continued, his tone light and deceptively casual, "I’ll leave you two to your... bonding. Just try not to kill each other before the big mission. You know, the one that requires you both pretending to get along?"

"Can’t wait," Nellie muttered, her voice dripping with sarcasm. She turned toward the exit, tossing her towel over her shoulder and shooting Bucky a parting glance. "You hear that? Apparently, we’ve got great chemistry."

"If by chemistry, you mean we annoy the hell out of each other, then sure," he replied evenly.

"Aw, you do care," she teased, her grin widening as she walked away.

Bucky caught the towel she tossed in his direction with ease. For a fleeting second, his expression softened, the faintest hint of a smile tugging at the corners of his lips. Shaking his head, he threw the towel onto the bench and muttered under his breath, "Reckless."

Across the Tower, in the dim glow of his workshop, Tony watched the interaction unfold on a holographic screen. He leaned back against a table cluttered with half-finished gadgets, a satisfied grin spreading across his face. "Oh, yeah," he said quietly, his tone conspiratorial. "This is gonna be fun."