AN: Why hello there, its been a long time since I've posted anything on ffn! But here I am and in a new fandom too. I've been pretty much devouring as much bnha fanfiction as possible since I caught up with the manga. Writing this pairing in particular was inspired by the story 'Total Command' by Epsilon110, so if you haven't read that yet then check it out. They're a much better writer than I am.

On another note, I have around 40k words of this story written and plan to release it in arcs to avoid feeling pressured by a schedule. So depending on the response I might end up just posting the whole arc at once. At which point I'll take as much time as I need to finish the second arc and start posting that when it's done, then the third and so on…

As with my other novel-length fic I prefer to write older characters to deal with scenes of a mature nature, so this will be an AU where UA is a University instead of a highschool. The only thing this changes is that every relevant character was born three years earlier. Every event that happened before cannon occurs at roughly the same time unless otherwise stated, ie. All Might was injured the same amount of time before the main cast attends UA.

Also! Characters may be highly OOC, this is a combination of my inability to write children accurately, as well as Katsumi simply being a different person than her canon counterpart. If she acted exactly the same as Bakugo does in the manga then I'd never be able to write a romance between them.

Enjoy.

Metallurgy

Prologue

Katsumi Bakugo had been a prodigy in every sense of the word, and by some twist of fate, was also my best friend.

Showing hints of unparalleled skill even at a young age, no one ever hesitated to tell her how lucky she was to be so talented, that she was so blessed. Most agreed that she would go far.

They were so blind.

Blind to the hours spent with scrunched eyebrows, diligently copying Kanji until they were just right. Oblivious to the scrapes and bruises from doggedly scaling to the tallest point on our preschool's jungle gym until she could do it with her eyes closed. All our classmates cared about was that Kacchan was the first in the class to make it up there in the first place.

It came as no surprise when at the age of four Katsumi ignited a classmate's shirt as she shoved him away in a schoolyard scuffle.

Well the situation itself was surprising. Even in a world full of superpowers, spontaneous combustion was usually cause for alarm.

But after calming a screaming toddler, no one was surprised that the fiery blond had developed a quirk to match her personality.

The soft pops and cracks of the sparks that danced across her palms had been beyond mesmerizing to me at the time. It had only cemented Kacchan's place as the coolest girl ever in my mind.

The reality was less elegant, but no less impressive.

She could secrete a substance from her sweat glands that performed much like nitroglycerin. Aside from the fact that it could be remotely detonated with a mere thought.

It was a near flawless amalgamation of her parent's quirks, seemingly engineered in its efficiency. Aunty Mitsuki could secrete glycerin from her skin, a comically innocuous abililty considering how similar the woman was to her daughter, but when paired with her husband's ability to oxidize his sweat, the result was… explosive.

Katsumi wasn't the first of our small class to develop her powers, but hers was undoubtedly the flashiest. A quirk with power and versatility piled into a convenient little package.

A hero's quirk.

Kacchan could be brash, short-fused and downright confrontational on her best day, but she would undoubtedly put it to good use.

Once she'd stopped accidentally lighting her assignments on fire.

Weeks passed, and one by one, the children in our small daycare started developing their quirk, every ability fascinatingly unique, yet none with the same raw potential as Kacchan's.

There were only a handful of us who had yet to manifest our quirk. I'd always wondered if their heads were plagued with the same dark thoughts as mine had been. It'd been reported that one fifth of the current world population was quirkless, but many of that number were the elderly of the previous generation.

The probability of being quirkless nowadays was incredibly unlikely. Highly improbable but not entirely impossible.

Katsumi and I drifted apart when it became apparent that my quirk wasn't showing up any time soon. Not that I really had any say in the matter, it was a miracle that she gave me the time of day in the first place.

At least that's what I thought at the time.

For months I satiated my hunger for learning about quirks by following the pros through online sites like heroTV, having already meticulously studied my classmate's abilities. I eventually learned to write myself, channeling my obsession, (and my frustration) into the very first volume of 'Hero Analysis for the future'.

But as fascinated as I was with the quirks of others, nothing would replace having one of my very own. The weeks passed and I felt the chasm between my best friend and I only grow wider.

I feared that I would be cursed with a label that would seal my fate for life. That I couldn't walk at Katsumi's side. That I wouldn't be gifted with the power to be a hero.

Until one day, I was.

Chapter One

oooOo Izuku oOooo

It was a clear spring morning and Midoriya Izuku had just begun his first year of primary school. The young child sat huddled in the space between a scuffed metal equipment shed and the fence that ran the length of the small elementary school's yard. It was a hiding spot easily overlooked, but being a boy of small stature, slipping into the tight space was easy as pie.

The reason he was hiding? Because he was a villain of course!

Well… he was playing a villain. The game was pretty much the main attraction for recess at Aldera primary school. Kids miming their favorite heroes' special moves chased down others who did their best 'evil villain' laughs. Such was the nature of a superpowered society. Letting children chase each other around the yard like maniacs was already tempting fate as it is, add in rapidly developing quirks and the control of emotionally unstable almost five-year-olds and you have a recipe for chaos.

To say Fubuki-sensei wasn't quite as strict as she could have been about quirk usage during recess would be a gross understatement. But you really couldn't blame the woman. If teachers were underpaid before the quirk revolution, then what were they now?

Izuku smiled lightly at the distant staccato cracks of Kacchan's quirk at work. A few months and she was already propelling herself around with small explosions like she'd been doing it for years. He wondered how all their friends missed the slight burn marks around her hands while they praised her acrobatic displays. Izuku knew for a fact that her body was resistant to her own explosions, it was one of the first thing's he'd noted on Kacchan's hero page. To think she would injure herself practicing in spite of that. Her dedication was frightening, and yet Izuku couldn't help but admire her with the same wide-eyed joy he had when they were younger.

"Oi… Deku," a voice said from behind.

Ah! He'd been found.

One offhand comment from Kacchan about the characters in his name and some of the crueler kids in their class had latched on to the insult with vicious glee. Being the last in the class without a quirk didn't help make many friends so the name stuck.

Izuku was sure she'd never even meant anything by it, but as perceptive as the young boy was, deciphering Katsumi's various glares was a skill he was still working on. She'd been… different lately.

Had she finally given up on hanging out with the quirkless loser?

"Oi, Deku! What the hell is this thing?" the voice said with a bit more heat.

Izuku flinched away from the voice and turned to see that it was Endo, one of the friends he'd run around with in the past before their quirks had complicated everything.

The taller boy's attention was not on Izuku as he initially thought, but instead poking his spindly, elongated fingers into… what was that?

Confusion came first. Endo-kun's quirk was long-fingers, not the most inventive name but that was to be expected as Izuku always thought the boy was a few crayons short of a full box.

But if this wasn't his then—

"It's finally happened." The words ghosted past his lips as he stared in wonder at the orb of shifting metal floating before his very eyes. It was around the size of a baseball, and bobbed and weaved through the air as if riding the waves of his disbelief. Izuku had never seen anything quite like it before, not in all his time spent analyzing quirks. His shoulders somehow managed to sag in relief and straighten with confidence simultaneously. It would be fair to say that he didn't know quite what to think.

He felt a tingling warmth starting to radiate from his gut. Was this what the other kids all felt? Could he be a hero that inspired people by the mere mention of his name? The orb shivered in response, sunlight refracting over its pearlescent surface.

Izuku paused, noting the odd behavior. Was it a response to his mood? He'd have to add that to the tests. So much to do! Could it be controlled? What was it made of? Is ther—"

"Hey look! Useless's got himself a quirk." The shout cut through Izuku's habitual rambling, and a spike of fear shot through the young boy. Most of the class had gathered around from the disturbance, and in his experience being the center of attention never ended well.

"Woah!" gasped a student with gills and webbed ears.

"Way cool! What's it do?" yelled another boy with an extra arm growing over his right shoulder.

The others began shouting over each other, all clambering to get a look at the spectacle.

Izuku shrunk slightly as the voices blended together, the many students starting to yell over each other. But this was loads better than the hushed whispers and careless words he'd endured for the last few months.

He shot a sidelong glance at Katsumi who had stayed surprisingly quiet. Her startlingly crimson eyes widened slightly as they moved from the orb floating timidly by Izuku's side before meeting his own. She glanced away immediately with feigned indifference, but Izuku had known the girl long enough to see the interest hidden beneath the surface. There was something else there as well, something he couldn't quite identify.

"Settle down, children," Fubuki-sensei chided with the patience of a saint. She turned to the green haired child, "Congratulations, Izuku, it seems you were just a late bloomer after all! Why don't you show the class your quirk!"

He faltered a for a moment under the intense scrutiny. "I… uh, I just now saw it myself so I don't really kno—"

"Can you make it move?!" shouted a boy in the back.

A flush spread across freckled cheeks. He just now got his quirk and they already wanted some kind of demonstration?

He furrowed his brows in concentration, hoping, pleading, for the wobbling orb of liquid metal to do something, anything. But no matter what he tried, from screaming commands in his head to gesturing wildly with his hands, the orb remained almost mockingly still. Having to perform on the spot wasn't really helping matters, but Izuku was certainly convinced by this point that his own quirk had it out for him.

Embarrassment was joined by shame as all Izuku's classmates all quickly lost interest.

Katsumi hesitated for a moment, that same, unreadable look on her face. Was she angry at him? Disappointed?

The girl's chaotic platinum blonde hair shook slightly as she finally turned away with a dismissive "Tch!"

He wouldn't lie, seeing her walk away so casually stung. He had held some hope that some of their friendship remained, especially now that he had a quirk, but it figured someone of her caliber wouldn't have wanted to be friends with someone like him.

His classmate's reactions might have crushed someone of weaker will, but Midoriya Izuku was going to be a hero. That was indisputable.

And now… now he had a quirk of his own. For nearly half a year he'd done nothing besides analyzing unique abilities, if there was one thing he was confident in, it was figuring out his own.

He strode back to the classroom with as much poise as his near five-year-old frame could manage. Izuku yanked out Hero Analysis for the Future, Volume One and turned to the first blank page. With a manic determination he wrote in bold, black letters across the top of the page.

Subject: Midoriya Izuku

Quirk: Quicksteel

ooOo Katsumi oOoo

"Shit shit shit SHIT!"

A harsh crack and a gout of flames licked harmlessly at the fire-retardant walls of the Bakugo residence, but the concussive force of Katsumi's rage rattled the windows of the small home.

"Oi Brat! The fuck did I say about explosions in the house!?" came the incensed yell of her mother from down the hall.

"Shut up you old hag," the girl grumbled under her breath.

"What was that?!"

"Love you, mother dearest."

Of all the skills she'd picked up in her short life, sarcasm was one of her favorites. It was perfect for covering up how much her Mom's inhuman hearing unnerved her. Bakugo Mitsuki certainly didn't need a quirk to be terrifying.

Katsumi had just arrived home after an eventful day at her primary school, and perhaps trying to burn her house down wasn't the most logical reaction to said events.

But damn it she was pissed.

She so was so close to getting the stupid nerd to stop throwing his life away.

She knew Izuku had the heart of the hero. Of course she did. Having spent the greater part of their childhoods together how could she miss his selfless nature. How kind he was to people even at the expense of his own happiness.

Katsumi recalled the very last time they'd hung out together. How he'd choked down his least favorite flavor of snack mix, just so she could have the spicy miso flavor. And how did she repay him?

A wave of guilt washed over her as she recalled the state of her friendship with the kind boy.

But she also knew how his kindness would get him killed one day.

Even being labeled a prodigy from a young age Katsumi had no illusions to the kind of life a hero lead. Hell, it was what had attracted her to being one in the first place. That, and the enthusiasm of a wide-eyed, green-haired kid that looked at her like she was the next All Might.

Constantly throwing yourself headlong into danger with no regard for your own safety was the life of a hero. The best heroes always came out on top.

But some didn't. If you didn't have the power to back up all that self-sacrifice, then what was the damn point?

As the weeks passed and Izuku's quirklessness seemed more inevitable, Katsumi's belief was only strengthened. She knew even being quirkless wouldn't put a stop to the boy's ambition. His selflessness was only matched by his stubborn streak a mile long.

"He'd probably have just called it a 'setback,'" Katsumi scoffed.

She stomped into her room before flopping to her bed in a heap.

"Why won't you just give up… Deku?" she sighed. The name tasted bitter on her tongue, a careless comment turned into a cruel taunt reused endlessly by their peers.

She was still learning her Kanji back then dammit!

Regret stabbed at her thinking back on how she'd been treating her friend these past few months. Where they were once inseparable, there was now a wide chasm between them. All her fault of course. She couldn't bare to take part in the bullying, but standing by while it happened, while her wonderful, selfless nerd of a best friend was harassed by their reject classmates, was just as bad if not worse.

Her palms crackled along with her agitation, the destructive power eager to be unleashed on those damn extras. She'd have to settle for her pillow, at least until one of those idiots gave her an excuse to throw down.

Katsumi had hoped that the constant bullying would be enough to discourage him from being a hero so he could put that big dumb brain of his to good use curing cancer or some shit.

She should have known better.

Not only did the nerd still want to be a hero, but he still looked at her with those same fucking eyes. Like she could do no wrong.

It sickened her. She didn't deserve that look, not after abandoning him to the cruelty of their classmates.

Just one more week, she had told herself, not for the first time since this had all started. But it had all been ruined, all by that shitty useless quirk!

Katsumi had convinced herself that Izuku was close to giving it all up. She wasn't sure exactly where they'd stand once he did, but she'd planned to deal with it when it finally happened.

That was all thrown out the window when the nerd showed up half way through a game of heroes and villains with a god damn quirk. A full four and a half months after the last kid in their class got theirs.

For a moment her blood had run cold. Had her actions the past months all been for nothing? But even before seeing what his quirk could actually do, or couldn't as it had turned out, she had reassured herself that it wouldn't have mattered. A quirk did not change someone's personality, and as selfless he was, Izuku was simply too timid to be a hero. If the nerd couldn't stand up for himself, how could he stand up for others?

Her conclusion was only reaffirmed a moment later when Izuku's quirk proved to be as weak as its owner. Not only would it reignite his drive to be a hero, but it would do absolutely nothing to keep him safe.

"Shitty floating blob," she growled, steeling herself for the drama that was sure to come.

Katsumi knew she didn't deserve his forgiveness, but she selfishly hoped he'd give it one day all the same.

ooOo Izuku oOoo

"It seems to be a radical mutation of your own quirk, Midoriya-san."

The doctor's office was typical. Scholarly and pristine came to mind describing the décor, but he'd always felt this place was too formal to ever be comfortable.

Izuku sat attentively, despite the quirk specialist ignoring him entirely in favor of his mother. He was used to such treatment by this point as adults tended to not take young children too seriously. Izuku didn't hold it against the man, it wasn't unreasonable to expect children to act like, well… children.

Izuku's mother stared the doctor down, a polite smile on her face as Izuku wondered not for the first time, which god he'd pleased to have such a nice mom. She coughed subtly and nodded towards her son before the doctor took a hint and addressed the boy himself. Izuku wiped at a tear threatening to fall and steeled himself. This was about his quirk, he had to be assertive!

And so, the questions began.

"Are we sure there's no influence from my father's quirk? He could breath fire," the boy asked excitedly. The doctor looked cautiously surprised but answered anyway.

"Whatever this material is," he started, peering curiously at the shiny orb bobbing serenely over the young boy's head. "Whatever it is, even though you currently have no willful control over it, given how it responds to your emotions we can assume that you have some sort of telekinetic connection to the material. A mutation of your mother's quirk is the most likely scenario, though its yet to be seen if you retain any temperature manipulation from your father." He sat thoughtfully for a moment, "these things tend to develop over time."

Izuku practically had stars in his eyes as terms like develop and temperature manipulation were thrown around like this doctor wasn't currently exceeding every meager expectation he set at the start of this visit. Of course, he had seen it first hand in some of his classmates even over the relatively short time since they'd had their quirks.

Even with his classmate's lukewarm reactions, it was still nice to receive some confirmation that there was a chance his quirk would not remain so frighteningly pointless. He took a deep breath, ready to dive back into the questions he'd prepared specifically for this visit.

"What did you mean 'whatever this material is'?"

"Ah, well you see the equipment we use in this building to test for heavy-metal toxicity in the bloodstream did not recognize the sample we took of your quirk. Its not so unreasonable as our tests are specifically geared to detect certain metals, but you'll have to send a sample to a more specialized facility to find out more."

Izuku nodded like a maniac, already planning his own experimentation. He panicked for a moment as the doctor checked his watch not for the first time that evening. Not yet! He had so many more questions, but the most important one of all sprang to the front of his mind.

"Sensei wait! With this quirk—c-can I be a hero with a quirk like this?" The question came out much more timidly than he had intended, but the doctor still managed to hear.

The man shrugged casually, "Maybe, I think that's up to you at this point. That concludes our allotted time, I have another appointment due in five minutes."

Izuku and his mother were escorted out of the office, the young boy with a spring in his step that wasn't present on the way in.

It may have taken an offhand comment from an apathetic quirk doctor for him to believe it, but for the first time in months, life was looking up for Izuku.