A/N: I know, I know. I'm practically a ghost left haunting this place, but sometimes I can't leave things well enough alone. Hopefully this story will make me get an epic comeback to dive back into writing the other stories left lying around and collecting dust bunnies. I know for sure some of you have been asking about stories like "Cutting Down the Ocean" and "Falling in the Plains of Time", but until then those stories will be left in the back burner for the time being. As for now, I'm gonna take a shot at the BNHA SI OC trope—but with a twist. Prepare your tissues, you're in for a ride.

Disclaimer: Boku no/My Hero Academia belongs to Kohei Horikoshi, my only claim is my own original character(s)!

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prologue

Origin Story: Part I

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Chaos Theory was something I once heard about in class.

An unpredictable change in routine, an extra or missing number of the equation, another result in a repeated experiment. People often misinterpreted it as the Butterfly Effect—they weren't entirely wrong. The common thread was that it had to with a change of something that resulted in a divergence of what was originally intended.

For example, I was a university student who followed a routine of going to my classes, taking a brief nap in my dorm between said classes, going out to eat something because my dorm mate had a sock hanging off the doorknob, and then coming back to my dorm to get some sleep and repeat the whole thing. Routine was safe, it worked well, it didn't leave me open to anymore stress than I already had from the tons of assignments I had to complete by the end of the first semester.

I had a pattern that I was comfortable with. It was a guidance system people developed all the time to keep in a straight path without unexpected mishaps. But the thing was, life was categorized as unpredictable for a good reason which was why there was going to be mishaps in someone's routine.

That's where the Chaos Theory came in, by throwing a damn wrench in your organized path of life.

The campus had a brief lock down due to a security situation where faculty warned students via text message not to come to class; trying to take a nap was nigh impossible no thanks to the awkward air that hung between me and my dorm mate and his girlfriend who also couldn't go to their classes, and I was left starving because the buses were so slow that by the time I reached the inner parts of the small town, it was overflowing with hungry students and tourists. The whole thing left me deranged, my clothes ruffled like an angry bird, and in a very poor mood that I didn't give two shits about the sock on the doorknob when I barged my way into my dorm room.

Routine was fucked, my order was in disorder, and I was absolutely fucking done with the day.

Which was how I ended up dying.

Having surprised the shit out of my dorm mate and his girlfriend from my sudden invasion to their sacred dance of mating, the damn idiot grabbed the nearest thing he could get his hands on then proceeded to chuck it at my face. Did I forget to mention that my dorm mate got into this school via high scholarships due to his mad arm swinging skills as a baseball pitcher?

Imagine the last thing you see is a baseball flying at you at speeds of 70 mph.

And that, ladies and gentleman, is the ridiculous story of how I died an equally ridiculous death.

It sucked. I was someone who was finally getting to do his own thing by his own rules, and I kind felt like I might've been going places, but sadly that didn't matter anymore. And another thing, I couldn't blame the idiot who accidentally killed me; sure, he was a jock, but my dorm mate was actually a pretty cool dude. He hadn't meant any harm, it's just his body acting on reflex because he hadn't expected anyone to step inside while he (and his girlfriend) were exposed.

So, the end it was.

But it wasn't the end like most people would say... and it wasn't like the hereafter as the other half believed from their gospels and bibles.

Me having died is not the crazy part of the story because the crazier bit is about what happened after my unforeseen death by flying baseball to the noggin.

Because, rather than it ending right then and there as most would assume, the wrench thrown in my life continued to follow me. It reverberated, it echoed, and it was from this push that it forced a motion of something unexpected elsewhere...

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Grete Gunnarsen cursed when she dropped her glass of red wine after blindly colliding against another body. "Faen!"

Her mother warned her not to get drunk, otherwise it would mess with her senses. However, given the situation she was in, Grete felt her mother would forgive her for wanting to drink herself to death.

"Sorry, sorry," the dark-haired man apologized as he knelt down near her feet, a napkin in hand to clean up the small mess she created. "Thank God it didn't get your dress, ma'am."

"It's fine." Grete replied sharply, waving at a nearby waiter to bring more napkins.

Sengoku Enzō looked up from where he was kneeling in front of the woman, and the pair's eyes connected.

Grete felt herself stare, taking in the man's sharp foreign features before settling on the dark blazer and slacks that was both to appear formal while also wearing a standard uniform to show that he was part of security for the men and women visiting her family from Japan. Meanwhile, Enzō couldn't help but stare up at the beautiful woman with the platinum blond hair and orange eyes that watched him with such intensity that he vaguely wondered if she could could see right through him.

He wouldn't be surprised if she could.

The majority of her family had a gift that came from Aksel Gunnarsen's second marriage. It was a trait that could have been of some use in the hero industry, but none of the women showed any interest on that particular field.

A waiter arrived with more napkins, joining Enzō on the floor to hurry in collecting the broken glass pieces so that no one would wind up getting injured. With the mess resolved, the dark-haired man stood up. Grete watched as he went up, and up, and up.

"Oh my."

The other man didn't seem bothered by her dumb remark. It actually kind of tickled his inside, a small quirk at the corner of his mouth expressing his amusement of her reaction to his height. It was a bit crooked but the action still made Grete flush a little which she viciously blamed the wine for.

"I can't be the first tall person you've come across." Enzō joked, feeling a bit foolish around the young woman. And could anyone blame him? She was gorgeous in her glittering dark azure dress, and it didn't help that there was a low cut on the back that showed plenty of skin.

The dark-haired man looked away, his face becoming flushed hot. He needed a drink. With lots of ice.

"Never up close. Besides, I don't really get a chance to meet a lot of people. I have to stay in certain circles."

She met more pompous and haughty brats than she had met patients. Most of her life revolved around dressing up for galas and charity balls her father forced her and her sisters to attend because they needed to present a perfect picture to the public. When she got older, however, she stuck close to school. After school, she continued her education into university which then led her towards the medical schools and then finally the hospitals. The experience invigorated her to reach out to strangers more than she ever did with the rest of men and women in the social gatherings.

Her eyes flicked over Enzō's torso, slowly trailing upwards until they met his honey-brown eyes.

The Sentinels, most called the Gunnarsen daughters.

Their eyes were their best quirks, more dominant from their mother's genes as they were born with heightened senses. Smelling things as good as a shark smelling a drop of blood in the vast ocean, their taste buds more sensitive to whatever ingredients they devoured, and their hearing so much keener than the average dog that they could easily easily identity a quiet mouse skittering about within walls of solid concrete while standing outside of said establishment.

Hearing Enzō's drumming heart this close up would be no problem for Grete.

Whiskey. He was going to drink some whiskey. With lots of fucking ice.

Looking back to where his entourage stood, he spotted Tsurugi and Ganta giving him looks. He should go back to them. Enzō was only here because he had a job to do, and he couldn't be doing his best if all he was doing was mingling with some elite lady who he had no business talking to like she was newfound crush he stumbled upon. Besides, she was going to get hitched in a few short months (this was rumored to be an engagement party, supposedly).

Her name was being called.

Mindful of the volume so it wouldn't disturb the party and its guests, it was still clear enough that it reached Grete's ears.

She frowned. It sounded more like an owner calling for his pet.

The bodyguard noticed her small strained look and looked over to spot a familiar man slowly making his way towards them: the would-be groom of the Gunnarsen lady. It was obvious for those who cared enough to look, to actually observe the scene in a broader sense, that this girl was not at all enthused with her engagement with the man. Most people liked to believe that arranged marriages were done and over with because this was modern times, but you only had visit certain rural countries, poverty-ridden areas, or attend a blue blood party to really get a glimpse of how men and women would treat trading vows as business transactions and not a promise of shared love.

The woman looked like she was contemplating whether or not it would be a good idea to fling herself out the balcony window just a few feet away from them. Enzō felt sorry for her, but it wasn't like there was anything he could do—

"Thirsty?" Grete suddenly asked, nervously pushing a lock of her hair behind her ear.

He couldn't help himself in watching the movement like a total creep, his eyes once more locked on the beautiful woman that he knew deep down would get him into so much trouble if he followed her to bar.

Dammit, her fiancé was coming closer.

And yet...

"Sure."

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She won't lie.

Anyone in her shoes would have hesitated, or felt doubt about what their actions. Like anyone in her position, she would have looked back and wondered if all this was worth the trouble... but then when she remember who was waiting for her at the altar, the young doctor felt her fears and anxiety erase. She turned away from her home one last time and reached for Enzō's hand as they both walked away hand-in-hand.

This wouldn't be the first time she disappointed her father, but it would be the last time he ever acknowledged her as his own daughter.

He didn't like that she preferred to stay a few extra years after completing the standard education in university, he didn't like that she pursued a career in the medical field after an inspiring presentation at the auditorium of her school, he especially didn't like that she spent so many hours in the hospitals surrounded by the sick and dying. It didn't matter that she was out there saving lives, what mattered was what he wanted for all his daughters.

The last straw was when Grete dismissed the man that would be her future husband.

There was a time when the old vulture was angry, something she had seen only rarely as he was a man more in love with his work than with his home life (the many times he's been married and divorced said as much), but when her father was enraged...

His lips curled back in and awful sort of sneer that he was almost unrecognizable to Grete. Her father looked like a man possessed by demons, making her feel like a little girl hiding underneath her bed sheets from the monster. The words that poured out of his mouth shook her to the core, make her light complexion grow pale as every word slammed into her. There were times when her father had called her a spoiled brat, an entitled child, but these vulgar words slammed at her like heavy carts of freight train.

A tease.

A slut.

A whore.

Her career was one thing he would have tolerated, but her refusal to marry the man chosen for her was not something her father would take lightly. Everything he had planned, to the man she should have been hitched to, to the merging of the groom's company to the family's, it was all ruined the moment she realized she liked Enzō's stupid jokes and dumb laughter. While the tall man was a bit intimidated by her, he didn't have much care about the privileged life her family led, never undermined her about her wants and wishes, and would match her evenly in a battle of wits.

Not once had he raised his volume when she got the last word, not once had he tried to "reign" her in as if she was an animal that needed to be controlled, not once was she treated like a prize that needed to be won. Not once did he ever lay a hand on her where no one could see the bruises left behind.

To Sengoku Enzō, she was merely Grete Gunnarsen.

The old vulture did things like freezing her bank account to the family money, excluded her from social gatherings when her sisters were attending, and kept most of her expensive possessions—as if the loss of such luxurious things mattered to her. She had her own account, she never really cared for the social gatherings besides the intimate ones she shared with her mother and sisters, and most of the time she wore her hospital scrubs.

That's when the old man snapped.

They expected Aksel Gunnarsen to shun her, to cut her off, to revoke her entry to her childhood home, to completely destroy her presence as if she never existed... what they didn't expect the old vulture to do was destroy any and all ties to Japan.

After all, if he couldn't get Grete back then he would get the man who took away his daughter.

Any company that was affiliated to the country was banned from doing any sort of business or trade. Quirk aid, tech, costumes, supplies, medical upgrades that happened every few years, all of it gone. And it didn't stop there. Aksel even had to go so far as using his influence to have other countries refuse servicing the Japanese, further isolating it from the other nations.

At first nothing happened, but then slowly things began to fall apart as Japan's stability started to crumble little by little until it snowballed out of control with catastrophic results.

It was beyond horrifying to watch it tear itself apart.

Enzō was forced to resign; whatever connections he had to his old home country, gone. He could already see how cold the reception would be back home, people looking at him with accusing eyes as if to say it was entirely his fault. The old Gunnarsen patriarch, so bitter and vengeful that he retaliated by destroying the man's reputation, throwing him towards the wolves where he would be ripped to shreds.

All this to get back at his "wayward" daughter who refused to obey his commands.

The old vulture wanted to ruin her life, he wanted to ruin her lover's, he wanted to ruin everything because they ruined his plans.

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Enzō watched his wife glow as the months rolled by, her hands coming to rest on the swollen area of her body.

He was going to be a father, and she a mother.

The nurses at the hospital would coo as she walked by, doctors from the maternal ward giving suggestions and sound advice to the nervous pair, and hospital patients offering their congrats (they needed it considering what awaited for them out in the real world).

The Gunnarsen patriarch, who often forcefully graced them with his unwelcome presence, would take one look at his daughter before frostily biting out that he hoped the babe in her belly would strangle itself from inside the womb. It took everything in Enzō not to attack the wretched bastard, otherwise attacking a high-profiled individual of his caliber who had money and connections wouldn't end well for him. He could end up a hundred years in solitary confinement if the wrinkly asshole had his way, ensuring that he would never see the light of day once the steel doors shut behind him.

Grete's eyes always fell down to her protruding belly, listening and hearing the movements done inside her through the thin skin that separated mother and child. He never wanted that look to fade away from his wife, to see the way her blossoming smile die at the reminder that her child was unwanted, that she disgraced her father with her actions by becoming a mother to the wrong husband.

Enzō resented the old vulture for haunting Grete like so.

It was hard enough that they would sometimes be harassed by people associated with the head Gunnarsen, but then it would mean that their child would face harsh discrimination for simply existing as the same breath as the old patriarch. No child of theirs deserved the scorn of some dreadful old man who didn't know when to let things be even after the years went by.

Grete's younger half-sister, Trine, was tasked with the unfortunate duty in marrying her ex-fiancé. It was cruel to see such a bright young lady have her life ruined by being bound to a diamond ring, but the marriage should have eased the old man off their backs. Yet even when the solution was solved, it didn't keep Aksel Gunnarsen away for long.

The bastard still flew circles overhead, waiting and biding his time to strike at them again, throwing Enzō's little family through another round of emotional turmoil and heartbreak. The man probably got off on this, smiling behind his contempt as he watched them struggle.

If he could, Enzō would take his family far away from Scandinavia in a heartbeat, but his options were limited. The Gunnarsen empire was vast and seemingly endless, Aksel's influence was almost everywhere that it would be difficult to apply for a visa. The only country that was free from the old vulture's influence was Enzō's birth country, but even that place wasn't considered safe for himself and his wife.

For the time being, he needed to keep his head low and wait; maybe things will cool down enough that he could try to consider the idea of returning to Japan with his little growing family in tow.

But right now, he had to do his best by protecting Grete and their unborn baby from the old vulture.

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It was one thing to watch from the other side how people reacted when meeting a newborn infant for the first time, but it was a whole different ball game when experiencing why people lost themselves looking at the tiny thing swaddled in soft blue blankets.

Their baby was the most beautiful thing they had ever seen.

The husband laughed as he cried while the exhausted wife clung to the infant close to her face because she couldn't stop looking at the tiny person she'd been waiting to meet for almost a year. The baby was a stranger to them but never had they felt so much love and connection as they did now for the small life they helped bring into the world. Proof was sitting right there, next to Grete and Enzō, oblivious to the overwhelming emotions he was inducing for merely existing.

Whatever shadow of doubts that had been clinging onto their shoulders immediately died the longer they stared, falling more and more in love with every passing minute as their son gave a soft mewl or weakly tug with his little precious pink hands when he managed to catch one or both of his parents' fingers.

He was beautiful. He was so beautiful.

"I love him." Grete sobbed as she felt the little fingers touch her tear-covered cheeks. "He's only a few hours old, but I already love him so much...!"

"Name?" a nurse asked, producing a clipboard when they realized neither parent wanted to part from their baby so soon.

Both husband and wife shared a look over their sleeping son's head. Not long ago, they had traded names back and forth, struggling to find what would be appropriate for their little newborn babe... but their search ended with an offered gift. It wasn't grand, but the gesture meant something and Grete and Enzō graciously accepted the gift.

The one and only act of love everyone inside the room would forever cherish.

"Kuzan," Grete finally answered, brushing a finger over the baby's soft dark hair that was beginning to flick up no matter how many times she brushed the stubborn locks down. "Kuzan Grímnir Sengoku."

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A few years earlier...

"Hey man?"

"Mm?"

"If you, like, had to pick a superpower, what would it be?"

I barely heard the question, too busy going over my laptop as my fingers typed then tweaked the sentences because I was a grammar freak about my work. The television in the background was low (my dorm mate was cool like that), but I could detect the faint sounds of explosions from what I could only assume was some action scene in whatever anime show he was watching. A love for all things anime and manga was what made the awkwardness between me and my dorm mate disappear, the both of sharing our likes and dislikes regarding the fascinating genre.

It still didn't stop me from feeling jealous now and then because of how popular and outgoing he was, not to mention how many different girls he's been with (meanwhile, my only relationship was back in my last years in high school and even that didn't count because it only lasted for about three days before my "girlfriend" called it quits).

"Hey," he called out again when I didn't answer.

I looked up from my desk, watching the colorful characters dancing around on the screen.

"I don't really keep up with that show." I told my dorm mate who was watching the screen with sharp attention, never missing the ball he kept tossing in the air. This guy had reflexes that I was honestly jealous of. Show off.

"But you have read and watched it, right?"

"Yeah." I turned back to my laptop. "Only because you can't shut up about it."

Due to all the work, both in the classroom and the job I got in working at a furniture store, I wasn't able to really check out the manga updates. Still, I was quite ahead enough to know some of the plots in the story.

"You didn't answer my question, you ass."

"What did you pick?" I asked instead. I was way too busy writing scary yet important things like listening devices implanted in smart televisions. Later on, someone was going to call me a crazy conspiracy theorist, but the paranoia would stay with them whenever they walked around their flat screens.

"I like the explosion power. Blowin' shit up! The only time I get to have that much fun is when I'm in my chemistry classes." I couldn't help but laugh a little at his answer.

"Or maybe you have the power to do chemicals, like combine elements and make things explode, freeze, spark, or whatever!"

"Ooh! Oh, that's even better!"

I typed away in my laptop, content in the silence that followed (besides the TV of course).

"Hey, you still didn't answer my question." I felt a hand nudge my side.

He wasn't going to leave me alone until I answered him. He was an asshole like that.

"Shit, I dunno! I'd probably have powers like Luffy, I guess." I shrugged.

"Wrong fandom, dude."

"It's still a superpower, ain't it?" I shot back. "Now shut up, I really got get this finished by tomorrow noon. My professor's been riding my ass because he didn't like my thesis on why university's are more interested in keeping sexual assaults quiet than dishing out the punishments to the perpetrators attending their school."

"Is he a creep? I bet he is. Bet you he likes to pick the pretty girls and make them stay behind in class for extra hour "sessions" over the dumbest things."

In the end, I didn't get to follow through with turning in my thesis since the following day involved a locked down campus, getting shoo'd out of my dorm room, going hungry before returning to my dorm where I subsequently died. Yet, even as I died, something about that moment changed. A disruption from my place which echoed so deeply that it caused a stranger from another time and place to lose her balance and slam into another body, resulting in the woman dropping her glass of expensive red wine.

Instead of heading towards the balcony where she would eventually be cornered by her intrusive fiancé, dragged back to the party and forced to dance with him, be led back home where he would slowly start to break her down as the countdown to their impending marriage grew shorter, gradually become a broken shell of a woman who was forced to withdraw from her job as a doctor at the behest of her new husband, endure years of emotional and physical abuse—she bumped into a stranger.

A stranger who was suppose to meet up with his entourage, keep a close eye on his charge, watch the crowd with detached apathy, and head back home without any hassle after the business venture with the Gunnarsens became a success. A stranger who would have been invited to the wedding of one of the Gunnarsen daughters, distantly admiring the platinum blond beauty who watched the crowd with a strained smile that didn't reach her sharp eyes. A stranger who was forgotten as he left behind the country to go back home with a new client waiting for him and the rest of the security detail.

An echo, a collision, a shattered glass. Two people who should have never crossed paths, exchanged words, and left together resulted in something unintended that the motion of the world scrambled to correct itself.

The Chaos Theory—an unpredictable equation that either added or subtracted the answer; would there be more butterflies or less in the world?

Would Grete Gunnarsen and Sengoku Enzō have met or not?

Whatever the outcome was suppose to be, somehow me dying and then being reborn as Sengoku Kuzan was the answer to that.