The Underground Champion

The Underground City pulsed with a feverish energy, its dimly lit corridors alive with the whispers of those living on the fringes of society. In this world beneath the surface, where sunlight never touched and hope was a scarce commodity, one name echoed through the dank air: Aaron Mustang.

At the heart of an improvised arena, surrounded by a roaring crowd, stood Aaron. His tall, lean figure cut an imposing silhouette against the flickering torchlight. Long, dark hair was pulled back into a messy bun, a few rebellious strands framing his sharp features. His emerald eyes, hard as the gems they resembled, scanned the baying crowd with a mixture of disdain and satisfaction.

Across from him lay his opponent, a mountain of a man now reduced to a groaning heap on the blood-stained floor. Aaron's chest heaved as he caught his breath, the exertion of the fight evident in the sheen of sweat on his tanned skin. He raised a taped fist, eliciting a deafening roar from the spectators.

"Ladies and gentlemen," a gravelly voice boomed over the cacophony, "your undefeated champion, the Green-Eyed Devil himself, Aaron Mustang!"

The Underground erupted. Coins and crumpled bills rained down into the arena, a meager fortune for those desperate enough to risk life and limb for entertainment. Aaron's lips curled into a sardonic smirk as he watched the frenzy. These people, so eager to forget their miserable existence, even if just for a moment – he understood them, even as he despised their weakness.

With practiced nonchalance, Aaron scooped up his earnings and pushed his way through the adoring crowd. Hands reached out to touch him, to feel the solidness of their champion, but he brushed them off with barely concealed irritation.

"Get off me," he growled, his voice low and dangerous. "Unless you want to be the next one kissing the floor."

The threat, delivered with such casual menace, was enough to part the sea of bodies. Aaron strode through the underground passages, his footsteps echoing off the damp stone walls. The further he got from the arena, the more his tough exterior seemed to crack, revealing glimpses of exhaustion and worry beneath.

Aaron's path took him to one of the many ramshackle markets that dotted the Underground. Here, amidst the pungent smells of unwashed bodies and dubious merchandise, he haggled for a loaf of bread and a bruised apple. It wasn't much, but in this world of perpetual scarcity, it was a feast fit for kings.

With his precious cargo secured, Aaron made his way to a dilapidated building that he called home. The stairs creaked ominously under his weight as he climbed to the third floor. At the end of a dark hallway, he paused before a battered door, taking a deep breath before entering.

"Rosy?" he called out softly, his gruff voice transforming into something gentler. "I'm home."

A small figure stirred on a threadbare mattress in the corner of the room. Rosy Mustang, all of ten years old, pushed herself up with trembling arms. Her gaunt face lit up at the sight of her brother, a smile breaking through the pallor of illness.

"Aaron!" she exclaimed, her voice barely above a whisper. "You're back early. Did you win again?"

Aaron's face softened as he knelt beside his sister, carefully arranging the meager pillows to prop her up. "Of course I won," he said, a hint of his usual bravado creeping in. "Your big brother's the strongest there is, remember?"

Rosy giggled, the sound transforming into a hacking cough that shook her tiny frame. Aaron's brow furrowed with concern as he gently rubbed her back, waiting for the fit to pass. When it finally subsided, he presented the apple with a flourish.

"Look what I got for you," he said, his voice forcefully cheerful. "It's even almost ripe."

Rosy's eyes widened at the sight of the fruit, a rare treat in their world of perpetual twilight. "It's beautiful," she breathed, reaching out with thin fingers to touch the apple's mottled skin.

Aaron carefully cut the apple into small pieces, feeding them to Rosy one by one. As he watched her eat, savoring each morsel as if it were the most delicious thing she'd ever tasted, he felt a familiar ache in his chest. In moments like these, the weight of responsibility pressed down on him, threatening to crush his spirit.

But Aaron Mustang wasn't one to buckle under pressure. He'd fought tooth and nail to keep Rosy alive, to provide for her in this godforsaken hellhole. He'd become the Underground's most feared fighter, cultivating a reputation for brutality that kept the wolves at bay. All of it – every punch thrown, every injury sustained, every shred of his humanity sacrificed – was for her.

As Rosy finished the last piece of apple, a sharp knock at the door shattered the peaceful moment. Aaron tensed, instinctively moving to shield his sister.

"Stay here," he murmured, rising to his feet with the fluid grace of a predator. Rosy nodded, her eyes wide with fear.

Aaron approached the door cautiously, his mind racing through possibilities. Debt collectors? Rival fighters looking for revenge? He'd made plenty of enemies in his rise to the top.

"Who is it?" he called out, his voice hard and challenging.

"It's me, kid. Open up."

Aaron relaxed marginally at the familiar voice. He unlocked the door, revealing a portly man with a receding hairline and a nervous demeanor. This was Marko, the organizer of the underground fights and Aaron's de facto manager.

"What do you want, Marko?" Aaron asked brusquely, blocking the doorway with his body. "If you're here for a cut of tonight's winnings, you can forget it. I need every coin."

Marko held up his hands placatingly. "Easy, champ. I'm not here for money. I've got news. Big news."

Aaron's eyes narrowed suspiciously. "What kind of news?"

Marko glanced nervously over his shoulder before leaning in closer. "The kind that could set you up for life," he whispered conspiratorially. "But not out here. Let me in, and I'll explain everything."

After a moment's hesitation, Aaron stepped aside, allowing Marko to enter. The older man's eyes darted around the sparse room, lingering for a moment on Rosy's huddled form before settling back on Aaron.

"Well?" Aaron prompted impatiently. "What's this big news?"

Marko took a deep breath, his excitement palpable. "You've been challenged," he said, a grin spreading across his face. "And not by just anyone. This is the big leagues, kid."

Aaron scoffed. "Big leagues? Down here? Don't make me laugh, Marko. Who could possibly-"

"The Survey Corps," Marko interrupted, his voice hushed with awe. "More specifically, humanity's strongest soldier himself – Captain Levi Ackerman."

The name hung in the air like a thunderclap. Even in the depths of the Underground, tales of Levi Ackerman's exploits had filtered down. The man was a legend, a living weapon in humanity's fight against the Titans.

Aaron's mind reeled. "You're joking," he said flatly. "Why would someone like that want to fight me?"

Marko shrugged. "Who knows? Word is he saw you fight today. Must have impressed him."

A spark of pride flared in Aaron's chest, quickly tempered by suspicion. "And what's in it for me? Besides a beating, that is."

"Money," Marko said simply. "More than you've ever seen. This fight... it's got people excited. The Survey Corps' strongest versus the Underground's undefeated champion. Bets are already pouring in."

Aaron's gaze drifted to Rosy, who was watching the exchange with wide, curious eyes. He thought of the medicine she needed, the better food, the chance at a life above ground where sunlight could chase the perpetual pallor from her cheeks.

"How much?" he asked, his voice low and intense.

Marko named a figure that made Aaron's breath catch in his throat. It was more money than he'd ever dreamed of, enough to change their lives forever.

"When?" Aaron demanded, already feeling the familiar pre-fight adrenaline coursing through his veins.

"Tomorrow night," Marko replied. "In the old cathedral. It's the only place big enough to hold all the spectators."

Aaron nodded slowly, his mind already calculating, strategizing. "I'll be there."

As Marko left, practically dancing with glee at the prospect of the money he'd make from this fight, Aaron turned back to Rosy. His sister's face was a mixture of excitement and worry.

"Are you really going to fight Captain Levi?" she asked, her voice trembling slightly.

Aaron knelt beside her, taking her small hands in his calloused ones. "I am," he said softly. "And I'm going to win. For us, Rosy. This is our chance to get out of here, to get you the help you need."

Rosy's grip tightened on his hands. "But he's so strong, Aaron. What if... what if you get hurt?"

A cocky grin spread across Aaron's face, a mask he'd perfected over years of hiding his fears and doubts. "Me? Get hurt? Come on, squirt. Don't you know your big brother's invincible?"

Rosy giggled, some of the worry leaving her eyes. "You're silly," she said, stifling a yawn.

"And you're tired," Aaron replied, gently easing her back onto the mattress. "Get some sleep. Tomorrow's going to be a big day."

As Rosy drifted off to sleep, Aaron sat beside her, his mind churning. The prospect of fighting Levi Ackerman both thrilled and terrified him. This was his chance to prove himself, to show the world – both above and below ground – what he was capable of.

But doubt gnawed at him. Levi's reputation was well-earned. The man was a killing machine, honed by years of battling Titans and humans alike. Aaron was good – the best the Underground had to offer – but was he good enough?

He thought of all the fights he'd won, the techniques he'd perfected, the raw strength and speed he'd cultivated through years of desperate survival. He'd never lost a fight, never even come close. But he'd also never faced anyone like Levi.

The day of the fight arrived with an electricity in the air that seemed to charge every shadow in the Underground. Word had spread like wildfire, igniting the imagination of every resident in this subterranean world. The undefeated champion of the underground fighting pits was to face off against humanity's strongest soldier. It was a clash of titans in its own right, a battle between two worlds that rarely intersected.

Aaron Mustang made his way through the winding passages of the Underground, his steps measured and purposeful. The usual cacophony of the hidden city seemed muted, as if the very air was holding its breath in anticipation. As he approached the old cathedral that would serve as the arena for this momentous fight, Aaron could hear the growing roar of the crowd within.

The massive wooden doors creaked open, and Aaron stepped into a sea of faces. The interior of the cathedral, once a place of quiet worship, had been transformed into a gladiatorial arena. Makeshift stands crowded every available space, packed to bursting with spectators from all walks of Underground life. The air was thick with the mingled scents of sweat, anticipation, and something else – hope, perhaps, or the intoxicating possibility of witnessing history.

As Aaron made his way towards the center of the cathedral, where a crude fighting ring had been erected, the crowd erupted. Cheers, whistles, and stomping feet created a deafening wall of sound that seemed to physically push against him. Hands reached out to touch him as he passed, as if some of his legendary strength might rub off on them.

"Mustang! Mustang! Mustang!" The chant rose and fell like waves crashing against a cliff.

Aaron's emerald eyes scanned the crowd, his face an impassive mask. He'd learned long ago not to let his emotions show before a fight. But beneath that calm exterior, his heart raced with a mixture of excitement and trepidation. This wasn't just another underground brawl. This was his shot at something more, a chance to change his and Rosy's lives forever.

As he reached the ring, Aaron's gaze fell upon the man who would be his opponent. Levi Ackerman stood in the opposite corner, his posture relaxed but alert. The Survey Corps captain was shorter than Aaron had expected, his slight frame belying the monstrous strength he was said to possess.

A smirk tugged at the corner of Aaron's mouth. He couldn't resist the urge to prod at the legendary soldier's composure.

"Well, well," Aaron called out, his voice carrying easily over the din of the crowd. "I've got to say, I expected humanity's strongest soldier to be a bit... taller."

A ripple of laughter ran through the audience, but Levi's expression remained unchanged save for a slight narrowing of his eyes. The captain's stoic reaction only spurred Aaron on.

"I've got to hand it to you, though," Aaron continued, making a show of looking around the transformed cathedral. "This place is spotless. I don't think I've ever seen anything this clean in the Underground."

Marko, who had materialized at Aaron's side, leaned in close. "That was one of the Captain's conditions for the fight," he muttered. "Insisted on cleaning the place himself."

Aaron's eyebrows shot up in genuine surprise. He turned back to Levi, a look of amused disbelief on his face. "You cleaned this place yourself? Man, you really are a psychopath, aren't you?"

If Levi was bothered by Aaron's taunts, he didn't show it. His steel-gray eyes remained fixed on Aaron, assessing and calculating.

With a flourish, Aaron grabbed the hem of his shirt and pulled it over his head, revealing a torso sculpted by years of brutal fights and harsh living. He tossed the garment into the crowd, where it was immediately seized upon by eager hands. Aaron turned in a slow circle, flexing his muscles and blowing exaggerated kisses to his adoring public.

"Alright, alright," he said, turning back to face Levi. "Let's get this show on the road. I've got plans tonight."

For the first time, Levi spoke, his voice low and intense. "Before we begin," he said, "tell me something, Mustang. What's your greatest desire?"

The question caught Aaron off guard, but he recovered quickly, his cocky grin never faltering. "My greatest desire?" he repeated, feigning thoughtfulness. "Well, if you must know, I've always dreamed of meeting a beautiful blonde girl to sweep off her feet and marry. You wouldn't happen to know any, would you, short stuff?"

A ripple of shocked laughter ran through the crowd. Even Marko looked nervous, shooting a worried glance between Aaron and Levi.

Levi's eyes flashed dangerously. "I see," he said, his voice cold. "In that case, let's end this quickly. I have more important matters to attend to than entertaining the fantasies of an underground thug."

The atmosphere in the cathedral shifted, the playful anticipation giving way to a tense, electric energy. Aaron and Levi moved to the center of the ring, where a nervous-looking official waited to begin the match.

"Fighters ready?" the man squeaked, looking as if he'd rather be anywhere else. At their nods, he raised his hand. "Then let the match... begin!"

The official's hand dropped, and in that same instant, Aaron launched himself forward. He'd built his reputation on explosive starts, overwhelming his opponents before they had a chance to mount a defense. It was a tactic that had served him well in the unpredictable world of underground fighting.

But Levi Ackerman was unlike any opponent Aaron had ever faced.

Aaron's fist, backed by every ounce of his considerable strength, rocketed towards Levi's face. In the split second before impact, Aaron allowed himself a moment of triumph. He could already see it – Humanity's Strongest Soldier, laid low by a single punch from the Underground's undefeated champion.

Then, faster than Aaron's eyes could track, Levi moved. The captain's arm came up in a perfect block, catching Aaron's punch on his forearm. The impact sent a shockwave through the cathedral, dust shaking loose from the ancient rafters.

For a moment, everything seemed to freeze. Aaron stared in disbelief at his fist, still pressed against Levi's unyielding block. He'd put everything he had into that punch, enough force to shatter concrete. And Levi had stopped it cold.

But Aaron Mustang hadn't become the Underground's champion by giving up easily. Gritting his teeth against the pain radiating up his arm, he pressed his attack. A flurry of punches and kicks rained down on Levi, each strike honed by years of desperate survival and countless fights.

Levi weathered the assault with an almost bored expression, his movements crisp and economical as he blocked or dodged each of Aaron's attacks. It was like trying to fight smoke – no matter how hard Aaron pushed, he couldn't seem to land a solid hit.

Frustration began to build in Aaron's chest. He'd never faced an opponent he couldn't at least touch. The crowd's cheers seemed to fade into the background as he focused every ounce of his concentration on trying to break through Levi's impenetrable defense.

In his growing desperation, Aaron overextended on a punch. It was a rookie mistake, one he hadn't made in years. But in that moment of frustration, his technique slipped.

Levi capitalized on the error with ruthless efficiency. A kick swept out, connecting with Aaron's extended leg. Pain exploded in Aaron's knee as his leg buckled beneath him.

Off-balance and reeling from the sudden pain, Aaron was helpless to defend against Levi's follow-up. The captain launched into a spinning kick, his boot connecting solidly with the side of Aaron's head.

The world exploded into a carnival of pain and disorientation. Aaron had been hit hard before, but this... this was something else entirely. It felt like he'd been struck by a steel girder rather than a human foot. His vision swam, dark spots dancing at the edges.

Through the haze of pain, Aaron was dimly aware that he'd been knocked to the ground. The stone floor of the cathedral was cool against his cheek, a stark contrast to the fire that seemed to be consuming the rest of his body.

With a monumental effort, Aaron forced himself back to his feet. His legs trembled beneath him, threatening to give way at any moment. But he refused to stay down. He was Aaron Mustang, the undefeated champion of the Underground. He didn't know how to quit.

Levi stood a few paces away, watching Aaron's struggles with detached interest. "Not bad," the captain said, his tone neutral. "Most people don't get up after a kick like that."

Aaron spat a mouthful of blood onto the floor. "I'm not most people," he growled.

A ghost of a smile flickered across Levi's face. "No," he agreed. "You're not."

The fight resumed, but it was clear to everyone watching that the dynamic had shifted. Aaron was on the defensive now, struggling to fend off Levi's lightning-fast attacks. Each block sent shockwaves of pain through Aaron's battered body, but he refused to give in.

In a moment of clarity between Levi's assaults, Aaron saw an opening. It was tiny, a fraction of a second where Levi's guard dropped ever so slightly. But for a fighter of Aaron's caliber, it was enough.

Summoning every last ounce of strength he possessed, Aaron launched a devastating right hook. Time seemed to slow as his fist arced towards Levi's exposed jaw. In that eternal moment, Aaron allowed himself to hope. Maybe, just maybe, he could turn this fight around.

His fist connected with a satisfying impact, and for a split second, triumph surged through Aaron's veins. He'd done it. He'd landed a clean hit on Humanity's Strongest Soldier.

But then he saw Levi's eyes. They weren't wide with shock or pain. They were narrowed, calculating. And Aaron realized, with a sinking feeling in his gut, that he'd fallen for a trap.

Levi's head snapped back with the force of the punch, but the movement flowed seamlessly into a brutal counter-attack. The captain dropped low, his leg sweeping out in a vicious arc.

Aaron, overextended from his punch and still reeling from the revelation that he'd been played, couldn't react in time. Levi's kick connected with devastating force, sweeping Aaron's legs out from under him.

As he fell, Aaron caught a glimpse of Levi's face. The captain's expression was grim, almost regretful. Then Aaron's head slammed into the stone floor, and the world went black.

* * *

Consciousness returned to Aaron in bits and pieces. First came the sensation of cold water on his face, shocking his system back to awareness. Then the pain hit – a symphony of aches and sharp agony that seemed to encompass every inch of his body.

Aaron's eyes fluttered open, immediately squinting against the harsh light of a nearby lantern. As his vision cleared, he found himself looking up at a familiar face. Marko stood over him, empty bucket in hand, concern etched across his features.

"Welcome back to the land of the living, champ," Marko said, his usual jovial tone subdued.

Aaron groaned, pushing himself up into a sitting position. The movement sent fresh waves of pain cascading through his body, but he grit his teeth and fought through it. As he took in his surroundings, he realized he was no longer in the main area of the cathedral. This appeared to be some kind of office – probably belonging to whatever priest still tended to this mostly abandoned place of worship.

"What happened?" Aaron asked, his voice rough. "How long was I out?"

"About ten minutes," a new voice answered.

Aaron's head snapped up, instantly regretting the sudden movement as pain lanced through his skull. Leaning against the far wall, arms crossed over his chest, was Levi Ackerman.

Memories of the fight came flooding back – the humiliation, the pain, the utter defeat. Aaron's fists clenched at his sides, shame and anger warring for dominance in his chest.

"Come to gloat?" he spat, glaring at the Survey Corps captain.

Levi's expression remained impassive. "If I wanted to gloat, I would have done it in front of the crowd," he said simply. "I'm here to make you an offer."

Aaron blinked, caught off guard by the unexpected statement. "An offer?" he repeated, suspicion coloring his tone. "What kind of offer?"

"I want you to join the Survey Corps," Levi said, his gray eyes intense as they bored into Aaron's.

For a moment, Aaron was sure he'd misheard. He looked to Marko, but the fight promoter seemed just as shocked by the declaration.

"You... what?" Aaron managed finally. "Is this some kind of joke?"

"Do I look like I'm joking?" Levi asked, his tone deadly serious.

Aaron struggled to wrap his mind around what was happening. "Let me get this straight," he said slowly. "You came all the way down to this shithole, challenged me to a fight, beat me to a pulp... all so you could recruit me?"

Levi nodded. "That's the long and short of it, yes."

A bark of laughter escaped Aaron's lips, quickly turning into a pained groan as the movement aggravated his injuries. "You're insane," he said, shaking his head. "Why the hell would I want to join the Survey Corps? In case you hadn't noticed, I'm not exactly soldier material. And I've got no interest in being Titan fodder."

"You're stronger than you give yourself credit for," Levi said. "Your technique needs work, but your raw potential is undeniable. With proper training, you could be an asset to humanity's fight against the Titans."

Aaron scoffed. "Thanks, but no thanks. I've got responsibilities here. I can't just up and leave to go play hero on the surface."

For the first time, a flicker of emotion crossed Levi's face – something that might have been understanding, or perhaps pity. "I know about your sister," he said quietly.

Aaron stiffened, his eyes narrowing dangerously. "What do you know about Rosy?" he growled.

"I know she's sick," Levi continued, unperturbed by Aaron's hostility. "I know you've been fighting in these pits to try and scrape together enough money to care for her. And I know that no matter how many fights you win down here, it will never be enough to truly give her the life she deserves."

The words hit Aaron like physical blows, each one striking at the fears and doubts he'd been harboring for years. He wanted to lash out, to deny Levi's claims. But he couldn't, because deep down, he knew the captain was right.

"If you join the Survey Corps," Levi went on, "you'll have access to resources you could never dream of down here. A home on the surface, with fresh air and sunlight. Proper medical care for your sister. Food, clothing, education – everything you've been fighting for all these years."

Aaron's mind reeled. The offer was almost too good to be true. But years of hard living in the Underground had taught him to be wary of anything that seemed too convenient.

"What's the catch?" he asked, his voice hoarse.

"The catch," Levi said, "is that you'll be putting your life on the line every time we go beyond the walls. The Survey Corps isn't for the faint of heart. We face death on a regular basis, and many of us don't make it back from our expeditions."

Aaron absorbed this information in silence. The prospect of facing the Titans was terrifying – he'd heard stories of their brutality, of the way they devoured humans without remorse. But as he thought of Rosy, of her frail body wracked by illness, he realized that staying in the Underground was its own kind of death sentence.

"If I say yes," Aaron said slowly, "you swear my sister will be taken care of? She'll get the medical attention she needs?"

Levi nodded solemnly. "You have my word," he said. "And I don't give that lightly."

Aaron closed his eyes, taking a deep breath. When he opened them again, there was a new resolve burning in their emerald depths.

"Alright," he said, his voice barely above a whisper. "I'll do it. I'll join the Survey Corps."

The words felt strange on his tongue, as if by saying them he'd irrevocably altered the course of his life. In a way, he supposed he had.

Levi pushed himself off the wall, approaching Aaron with measured steps. He extended a hand, his steely gaze never wavering. "Welcome to the Survey Corps, Mustang."

Aaron stared at the offered hand for a moment, the weight of his decision settling heavily on his shoulders. With a deep breath, he reached out and clasped Levi's hand, sealing his fate. The handshake was firm, a silent acknowledgment of the challenges that lay ahead.

As their hands separated, Aaron couldn't help but notice the strength in Levi's grip. It was a stark reminder of the gap between them, a gap he would need to close if he hoped to survive in the world above.

"So, what now?" Aaron asked, his voice a mixture of trepidation and barely concealed excitement.

Levi's expression remained impassive, but there was a glint in his eye that hinted at approval. "Now, we prepare. You'll need to say your goodbyes and gather whatever belongings you wish to bring. We leave for the surface at dawn."

The reality of the situation began to sink in for Aaron. Dawn. In just a few short hours, he would be leaving the only world he'd ever known. The thought was both exhilarating and terrifying.

"Wait," Aaron said, a sudden panic gripping him. "What about Rosy? I can't just leave her here while I go off to the surface."

"Your sister will be coming with us," Levi assured him. "I've already made arrangements for her to receive medical care once we reach the surface. She'll be well looked after while you undergo your training."

Relief washed over Aaron, easing some of the tension in his battered body. "Thank you," he murmured, the words feeling inadequate to express his gratitude.

Levi nodded curtly. "Don't thank me yet. The road ahead won't be easy. You've got a lot to learn, and not much time to learn it. The life of a Survey Corps soldier isn't for the faint of heart."

"I'm not afraid of hard work," Aaron said, a hint of his usual bravado creeping back into his voice. "I'll become strong enough to take on any Titan you throw at me."

A ghost of a smile flickered across Levi's face. "We'll see about that. For now, focus on recovering from our little sparring session. You'll need to be in top form for the training that lies ahead."

As if on cue, Aaron's body reminded him of the beating it had taken. Every muscle ached, and he was sure he'd be sporting some impressive bruises come morning. But the pain was a reminder of how far he had to go, and it only strengthened his resolve.

"Marko," Levi said, turning to the fight promoter who had been watching the exchange in stunned silence. "I trust you can help Mustang gather his things and settle any affairs he might have here in the Underground?"

Marko nodded quickly, seemingly relieved to have something to do. "Of course, of course. I'll make sure everything's taken care of."

"Good," Levi said. He turned back to Aaron. "I'll meet you at the entrance to the Underground at first light. Don't be late."

With that, the captain turned and strode out of the office, leaving Aaron and Marko alone with the echoes of all that had transpired.

For a long moment, silence reigned. Then Marko let out a low whistle. "Well, I'll be damned," he said, shaking his head in disbelief. "You sure know how to make an exit, kid. From Underground champ to Survey Corps soldier in one night. It's like something out of a story."

Aaron chuckled weakly, wincing as the movement sent a fresh wave of pain through his ribs. "Yeah, well, let's hope this story has a happy ending."

As the reality of his decision settled in, Aaron's mind raced with all that needed to be done. He had to tell Rosy, pack their meager belongings, say goodbye to the few friends he'd made in this harsh world. It was overwhelming, but beneath the anxiety, a spark of hope burned bright.

For the first time in years, Aaron Mustang dared to dream of a future beyond the dim corridors and brutal fight pits of the Underground. A future where Rosy could breathe fresh air and feel the warmth of the sun on her face. A future where he could make a difference, not just for his sister, but for all of humanity.

As he pushed himself to his feet, ignoring the protests of his battered body, Aaron felt a new strength coursing through him. The strength of purpose, of a goal beyond mere survival.

"Alright, Marko," he said, his green eyes blazing with determination. "Let's get to work. We've got a lot to do before dawn."

The next few hours passed in a whirlwind of activity. Aaron and Marko made their way through the winding streets of the Underground, tying up loose ends and saying hasty goodbyes. News of Aaron's defeat and subsequent recruitment spread quickly, eliciting a mixture of awe, envy, and in some cases, resentment from the denizens of the hidden city.

When they finally reached the small, dilapidated apartment that Aaron called home, a new challenge awaited: telling Rosy about the drastic change in their lives.

Aaron pushed open the creaky door, his heart heavy with a mixture of excitement and apprehension. "Rosy?" he called softly. "You awake, squirt?"

A small figure stirred on the threadbare mattress in the corner. Rosy pushed herself up, her pale face lighting up at the sight of her brother. "Aaron!" she exclaimed, her voice weak but filled with joy. "You're back! Did you win your big fight?"

Aaron's heart clenched at the innocent question. He crossed the room in a few quick strides, kneeling beside his sister's bed. "Not exactly," he said, forcing a smile. "But something amazing has happened, Rosy. Something that's going to change our lives forever."

As gently as he could, Aaron explained the events of the night – his defeat at Levi's hands, the offer to join the Survey Corps, and their impending move to the surface. He watched Rosy's expression carefully, trying to gauge her reaction to this sudden upheaval of their world.

To his surprise and relief, Rosy's face lit up with wonder and excitement. "We're really going to the surface?" she asked, her voice filled with awe. "We'll get to see the sun and the sky and everything?"

Aaron nodded, feeling a lump form in his throat at his sister's unbridled joy. "That's right, squirt. And you'll get to see real doctors who can help you get better. No more damp, dark Underground for us."

Rosy threw her arms around Aaron's neck, hugging him tightly despite her weakness. "Thank you, big brother," she whispered. "I always knew you'd find a way to get us out of here."

As he held his sister close, Aaron felt a renewed sense of purpose wash over him. This was why he had agreed to Levi's offer. This was why he would face the terrors that awaited beyond the walls. For Rosy, for the chance to give her the life she deserved, he would take on the entire world if he had to.

The rest of the night passed in a flurry of packing and preparation. Their belongings were few – some clothes, a handful of treasured mementos, and the meager savings Aaron had squirreled away over the years. By the time the first hints of dawn began to filter down into the Underground, they were ready.

Aaron stood at the entrance to the Underground, Rosy cradled in his arms and their small bag of possessions slung over his shoulder. Marko stood beside them, uncharacteristically somber.

"Well, kid," the fight promoter said, his voice gruff with emotion, "I guess this is it. You take care of yourself up there, you hear? And don't forget about us little people down here in the dirt."

Aaron managed a wry smile. "As if I could ever forget this place," he said. He shifted Rosy's weight to one arm, extending his free hand to Marko. "Thanks for everything, old man. I wouldn't have made it this far without you."

Marko clasped Aaron's hand firmly, then pulled him into a brief, fierce hug. "Go show those surface dwellers what Underground tough really means," he said as he pulled away, his eyes suspiciously bright.

The sound of approaching footsteps drew their attention. Levi appeared, his Survey Corps cloak billowing behind him. "It's time," he said simply.

Aaron took a deep breath, tightening his hold on Rosy. This was it. The moment that would change everything.

*****

The sun beat down mercilessly on the training grounds, its harsh rays reflecting off the dusty earth and creating a shimmering haze in the air. Rows upon rows of recruits stood at attention, their backs ramrod straight and faces set in determined expressions. Among them, looking decidedly less enthusiastic, stood Aaron Mustang.

The coarse fabric of the trainee uniform chafed against Aaron's skin, a constant irritation that only fueled his growing sense of frustration. He shifted his weight from one foot to the other, trying to find a comfortable position in the stifling heat. As he stood there, sweat beading on his forehead and trickling down the back of his neck, Aaron's mind drifted back to his conversation with Levi just days ago.

---

"Why the hell do I have to go through basic training with these greenhorns?" Aaron had demanded, his voice echoing off the stone walls of Levi's office. "I thought you recruited me for my fighting skills, not to play soldier with a bunch of kids."

Levi's steel-gray eyes had met Aaron's heated glare with cool indifference. "It's only three months, Mustang. In that time, your sister will be well cared for, receiving the best medical attention we can provide."

Aaron's fists had clenched at his sides, the mention of Rosy simultaneously calming and agitating him. "And what about my training? I thought I was supposed to be preparing to fight Titans, not learning how to polish boots and salute properly."

"You need to learn the basics," Levi had replied, his tone leaving no room for argument. "Fighting Titans isn't just about raw strength or street brawling skills. There's strategy, teamwork, and specialized equipment you need to master. The Training Corps will give you that foundation."

Aaron had scoffed, crossing his arms over his chest. "And what if I don't make the cut? What if I'm not 'selected' at the end of all this? What happens to Rosy then?"

For the first time, a flicker of emotion had crossed Levi's impassive face – something that might have been amusement, or perhaps exasperation. "Don't be ridiculous, Mustang. If I personally recruited you, it's because I see potential in you. You'll make it through the training. The question is, will you make the most of it?"

---

A sudden increase in volume from the front of the formation snapped Aaron back to the present. He blinked, focusing on the source of the commotion. A bald, intimidating man – Instructor Keith Shadis, Aaron recalled – was currently engaged in a verbal assault on a brown-haired girl who looked like she wanted the earth to open up and swallow her whole.

"And what do you think you're doing, recruit?" Keith's voice boomed across the training grounds. "Stealing food on your first day? Do you think this is some kind of vacation?"

The girl – Sasha, if Aaron remembered correctly from the earlier roll call – trembled visibly. "I... I was hungry, sir," she stammered, a half-eaten potato clutched in her shaking hands.

Keith's face turned an alarming shade of red. "Hungry? HUNGRY? I'll show you hungry! You'll run laps until dawn, recruit! Maybe then you'll learn the meaning of discipline!"

As Sasha took off running, tears streaming down her face, Aaron couldn't help but shake his head in disbelief. "Man, this guy really knows how to yell," he muttered under his breath, unable to stifle a yawn that had been building for the past hour.

Unfortunately for Aaron, Keith Shadis possessed hearing as sharp as a hawk's. The instructor's head snapped around, his eyes locking onto Aaron with predatory intensity. In a flash, he was standing before the former Underground fighter, looming over him like an angry colossus.

"Is there something boring you, recruit?" Keith growled, his face mere inches from Aaron's. "Is my training regimen not exciting enough for you?"

A smirk tugged at the corner of Aaron's mouth, his natural sarcasm bubbling to the surface despite his better judgment. "Oh, it's not that at all, sir," he said, his voice dripping with false innocence. "It's just that I usually get my full eight hours of sleep, you know? Helps keep me sharp and prevents... unfortunate hair loss."

A collective gasp rippled through the ranks of recruits. Even the birds seemed to fall silent, as if the very air was holding its breath in anticipation of Keith's reaction.

The instructor's eyes narrowed dangerously. "Oh, is that so?" he said, his voice deceptively calm. "And who might you be, recruit? What's your name?"

Aaron straightened up, bringing his fist to his heart in an exaggerated salute. "Aaron Mustang, sir!" he announced, his green eyes twinkling with mischief. "Hailing from the lovely Underground city. Sixteen years old, fond of blonde girls and my luscious locks. At your service!"

Keith's eye twitched, a vein pulsing visibly on his forehead. "Ah, so you're the one Levi Ackerman personally recommended," he said, his voice dripping with sarcasm. "Don't think that gives you any special privileges here, Mustang. You're just another maggot to me."

Aaron's grin widened. "Oh, perish the thought, sir! I wouldn't dream of expecting special treatment. I'm just here to, you know, let my personality bloom. Isn't that what they say about teenagers? We're in our rebellious phase."

For a moment, it seemed as if Keith might spontaneously combust. His face turned an alarming shade of purple, and when he spoke, it was in a roar that could have woken the dead. "REBELLIOUS PHASE? I'LL SHOW YOU REBELLIOUS! YOU'LL RUN LAPS AROUND THIS FIELD UNTIL NIGHTFALL, MUSTANG! MAYBE THAT'LL TEACH YOU SOME RESPECT!"

As Aaron took off running, he couldn't help but feel a twinge of satisfaction. Sure, he was in for hours of grueling exercise, but at least he'd livened things up a bit. Plus, he reasoned, all this running would only make him stronger. By the time he faced the Titans, he'd be unstoppable.

Hours passed, the sun arcing across the sky as Aaron's feet pounded the dusty earth. His lungs burned, his muscles screamed in protest, but he pushed on, driven by a mixture of stubbornness and the burning desire to prove himself. As twilight began to paint the sky in shades of orange and purple, Aaron finally allowed himself to collapse.

He hit the ground with a soft thud, chest heaving as he gasped for air. To his surprise, he found he wasn't alone. Sprawled out beside him was Sasha, the potato thief from earlier, looking just as exhausted as he felt.

"Water," Sasha croaked, her voice barely above a whisper. "Food. Anything. Please."

Aaron managed a weak chuckle. "Join the club," he panted. "I think I've sweated out every drop of moisture in my body."

Just as Aaron was contemplating the very real possibility that he might die right there on the training field, a shadow fell across his face. He squinted up, his vision blurry with exhaustion, to see a figure haloed by the setting sun.

For a moment, Aaron thought he must be hallucinating. The figure before him looked like an angel, with golden hair catching the last rays of sunlight and kind blue eyes filled with concern. Then the "angel" spoke, and Aaron realized it was very much real.

"Are you two alright?" the girl asked, kneeling down beside them. In her hands, she held a canteen of water and what looked like a few pieces of bread. "Here, you must be thirsty."

Aaron and Sasha both stared at the offered sustenance as if it were the most precious treasure in the world. With trembling hands, they accepted the gifts, gulping down water and tearing into the bread with ravenous abandon.

"You're a lifesaver," Aaron said between mouthfuls. "A real angel. What's your name?"

The girl smiled, a soft, gentle expression that seemed to light up her whole face. "I'm Christa," she said. "Christa Lenz. And you're Aaron, right? The one Instructor Shadis was yelling at earlier?"

Aaron grinned, some of his usual cockiness returning now that he had food and water in his system. "The one and only," he said with a wink. "Aaron Mustang, Underground champion and professional troublemaker, at your service."

Before Christa could respond, another voice cut through the air, sharp and sardonic. "Well, well, making friends already, Christa? Or is this just your good deed for the day?"

Aaron looked up to see another girl approaching, tall and lanky with dark hair and a perpetual smirk on her freckled face. He vaguely remembered her name being called during roll call – Ymir, if he wasn't mistaken.

"I'm just helping out," Christa said, a slight defensiveness creeping into her tone. "They've been running all day."

Ymir's smirk widened. "Always the saint, aren't you? Don't tell me you're not expecting anything in return."

Aaron, never one to stay quiet for long, piped up. "Hey now, don't go insulting my guardian angel," he said, flashing a charming smile at Christa. "Though if you're offering to take her place, I'm afraid I'll have to decline. I prefer my angels a little less... prickly."

Ymir's eyes narrowed dangerously. "Watch it, Underground rat," she growled. "You don't want to make enemies on your first day."

Before Aaron could retort, Sasha let out a soft groan and slumped over, apparently having reached her limit. Christa gasped in concern, but Ymir just rolled her eyes.

"Great, now we've got a passed-out potato girl to deal with," Ymir grumbled. To everyone's surprise, she bent down and scooped Sasha up in her arms with surprising ease. "I'll take her back to the barracks. Consider it my good deed for the year."

As Ymir trudged off with the unconscious Sasha, Christa called after her, "What are you doing, Ymir?"

"What does it look like?" Ymir called back over her shoulder. "I'm being a saint, just like you. Don't wait up!"

With Ymir and Sasha gone, Aaron found himself alone with Christa. He turned to her with a grin, his green eyes twinkling with mischief. "So, angel," he said, his voice dropping to a playful whisper. "Since I'm too weak to feed myself, think you could help a poor, starving recruit out? You know, for your good deed of the day?"

Christa blinked, a blush creeping across her cheeks. "I... what?"

Aaron held up a piece of bread, his expression a comical mixture of pleading and roguish charm. "Come on, just a little bite? I promise I don't bite... unless you want me to, that is."

For a moment, Christa looked torn between amusement and exasperation. Then, to Aaron's surprise and delight, she let out a soft laugh. "You're incorrigible, aren't you?" she said, shaking her head. "Fine, one bite. But then you're on your own, Mr. Underground Champion."

As Christa held the bread to his lips, Aaron couldn't help but feel a surge of triumph. Sure, he was exhausted, sore, and facing months of grueling training. But in that moment, with the sun setting behind them and the promise of new friendships (and potential romances) on the horizon, Aaron Mustang felt like he could take on the world.