In one world, a demon who'd lived for half a millennium fought his final battle.
After felling humans numbering in the thousands, he met his end not at the hands of a god-like opponent whose innate talents surpassed the moon breathing techniques that had been forged over centuries, but rather the combined efforts of opponents both weak and strong, human and demon. He found no peace, experienced no comfort, and gained no deeper understanding of his purpose in life. When he was sent to hell to pay for his crimes, he was dragged clawing and resisting, never once accepting the fate he himself had orchestrated.
But eventually, his fruitless efforts ceased.
…
In one world, Kokushibou closed his eyes for the last time.
And in another, Midoriya Izuku opens all six of them.
…
From the moment he was born, the nurses said he was cursed.
Though quirk mutations weren't a rarity in the world they lived in, never before had the doctors seen one quite as peculiar as Midoriya Izuku's. No one in the Midoriya family line could be considered a mutant, nor were they completely silent and still upon birth, and yet Izuku was both.
At first, the doctors were concerned that something had gone wrong during the procedure, and the baby had been stillborn. The list of reasons the baby could have died were endless, and ever since quirks entered the equation no doctor could be certain of a newborn's safety during delivery. But when the attending doctors rushed to provide medical care to the newborn in the hopes that their life could be saved, they were met with six piercing eyes that stopped them in their tracks.
Eyes that saw too far, moved too fast, knew too much.
But worst of all was their color: Blood red, and with chilling yellow irises.
Mutation quirks weren't a rarity in today's world. Many of the country's top heroes bore quirks that drastically altered their physiology relative to a normal human's.
And yet for some reason, in that moment, those three pairs of eyes struck fear and despair into every person that met them. Almost as though everyone in the room was present for the birth of a demon.
Later that day, Midoriya Izuku's quirk was officially listed as "Six Eyes".
…
…Where am I…
Is this hell?
Hell seems to be far brighter than I expected…
No… I do not feel enough pain for this to be hell…
Focus… Look beyond what appears to be…
See the truth for what it is….
... a white room?... With… healers?
Have the demon hunter corps taken my body for the sake of experimentation?
Is that why my form feels incomplete?
No… Their bodies are not trained enough to be demon hunters… and why does that one's lungs have signs of burns? It is almost as though flames have been birthed from his breath…
…
I… see…
… It seems… the times… have changed.
. . .
Sometime later, in an apartment in Mustafu, two friends met for tea.
After listening to Inko's babbling for the better part of an hour, Mitsuki Bakugou puts down her cup. "And he hasn't made any noise?" she asks. "Not even a whine? Hell, compared to mine he's practically heaven in a blanket, wanna switch?"
Inko, for the first time since they sat down, looks up to meet her eyes. "Mitsuki, please. I-I'm being serious. It's b-been weeks and I don't know what to d-do. Hisashi is doing some research on developmental d-disorders but the doctors aren't really sure and I, well I-I just-"
"Inko, Inko, relax. The kid is gonna be fine. And even if he never says a word, Katsuki's going to need someone who can balance his screaming out, otherwise both of our eardrums are going to be blown before his quirk even comes in."
"I-I'm just w-worried is all. N-None of the books I've read said a-anything about something like this h-happening. And-and those eyes…" she begins to tear up once again.
Mitsuki flashed her a comforting smile. "Personally, I think his eyes are the coolest things I've ever seen, but I get why you and Hisashi are a bit freaked out. I mean, neither of your families have histories of mutations, and none of their quirks come close to little Izuku's. But no matter what his quirk is, he's still your son. That's got to count for something right?"
Inko stops crying just long enough to respond. "I suppose so. I just hope he doesn't have trouble making friends. Children can be so cruel…"
"As if Katsuki would ever let that happen! With the amount of trouble he's already giving me I can't imagine what he'd do to a bunch of prejudiced brats!" She laughs.
…
Meanwhile, in a different room, Kokushibo was coming to terms with the new life he had been given as Midoriya Izuku. Though he was limited to the space of his crib, his mind wandered to the distant past and the confusing present.
It appears that in this new world blood demon techniques have become a normal aspect of human life and are known as quirks… Is it possible that Muzan-sama was able to overcome his weakness to the sun and proliferate his blood across all of Japan? If so, then he is likely still alive and can return me to my former glory… as it stands, I have neither proficiency with the blade nor the strength and regeneration from demonhood…
Izuku looked down at his arm. Flabby, short, and slow, it resembled nothing like the arm he had trained for over four hundred years. My biology appears to be entirely human. None of my demonic abilities remain; even my mark has vanished. Save for my eyes, my senses have also been dulled significantly. He puts down his arm. How many years has it been since I was this limited in functionality…
His vision returns to the ceiling, looking for something to maintain his attention. Before Muzan-sama granted me demonhood I was more than capable of defending myself, and yet here I am, more powerless than I've ever been before. It may be a long while yet before I can return to my prime.
A frown appears on his face. It seems it will take some time before I am able to train with the same level of freedom that I had as a demon. Training will have to be limited to wooden swords, and practice cannot lead to the permanent injury of whatever opponent I face. If I draw too much attention from the authorities early in my training, It will be more difficult to perfect my techniques in the future…
Suddenly, he came to a realization.
The future? What do I want to do in the future?
It was not something he had considered up until that moment.
In my past life my goals were simple. Perfect my techniques and preserve them. My nature as a demon allowed me that luxury that humanity didn't. I thought that my strength was enough to sustain that lifestyle… However, those demon hunters proved me wrong. Those humans, whose skills, techniques and abilities were far inferior to mine managed to defeat me, a feat I never even thought possible… At least not after…
The sudden image of a familiar face flashes through Izuku's mind. At the same time, his heart rate drastically increases.
Enough. Reminiscing is pointless. Focus on the future.
With nothing better to do than ponder his possible paths, Izuku lies in the crib until his mother collects him for feeding. His father returns home, his two parents pretend everything is fine, and all the while Izuku's mind was elsewhere. Eventually, after he's put to bed, he comes to a conclusion.
For the time being, I need to gather information about my surroundings so I can better prepare to streamline my training regime. I won't be able to reach a fraction of my former skill with my current biology, however I can become strong enough to pursue other avenues of ascension. After all, those demon hunters were mere humans and they managed to surpass me.
Izuku's thoughts returned to the demon hunters who successfully fell him.
What error did I commit in that battle that led to my defeat? Certainly hubris; Had I eliminated the mist pillar and the half-demon as soon as the opportunity presented itself, I never would have been overwhelmed by their combined efforts.
Pride has always been a flaw of mine. Perhaps in my pursuit of perfecting my forms I neglected to improve my character.
A distant memory. An open field.
"We are not so great, you and I. We are but a small fragment in humanity's long history."
A vein made itself visible on the infant's forehead.
How could he say that? A voice hissed in Izuku's head. How could he be so calm at the idea of his efforts being surpassed? His very existence? Did he not value the gift he had been given? Or did he truly believe his worth to be inferior to that of a successor?
A faint smile, eyes seeing a brighter tomorrow.
"One day the children of tomorrow will surpass us and climb to even further heights."
Izuku closed his eyes.
No. Not inferior. Not weaker. Yoriichi believed that future generations would not only reach our levels, but surpass them. But how were you so sure brother?
Izuku's eyes closed in the darkness.
What kind of future did you envision at that moment that made you smile so?
…
A blood moon in the sky. Two brothers without bond meet for the last time.
Both thinking the same thought:
"This is heart-wrenching, brother."
But while one thought it with sincerity, the other thought it with disgust.
A final goodbye.
An unfinished duel.
Hate.
HATE.
HATE.
Izuku woke up in a cold sweat, staring at an unfamiliar ceiling. Only after a few seconds did he realize that he was not standing in a field with a sword in his hands, but was instead lying in a crib, defenseless and alone. He wiped the sweat from his face to the best of his ability and returned to his slumber, too tired to notice the tears his fingers had felt.
…
After his morning meal, Izuku was returned to his crib, allowing his thoughts to wander to his next steps.
As it stands, my combat potential is far lower than it was in my previous life. If by some unfortunate circumstance I am truly unable to reclaim my former strength then I cannot allow my techniques to fall into obscurity.
Once again, his brother's words resound in Izuku's head:
"One day the children of tomorrow will surpass us and climb to even further heights."
Izuku shuts his eyes in the vain hope that the action would halt his train of thought. When he realizes it wouldn't he slowly opens his eyes.
Perhaps there was truth to his words. With the variety of blood demon arts, or quirks, available today, surely some individual has the potential to succeed my breathing technique.
Izuku's final memories as Kokushibo flash through his eyes. And there would be no harm in having that insurance in case I met a premature end.
After a few more minutes, Izuku came to a conclusion. As unfortunate as it is, it seems it is necessary for me to search for a worthy successor to the Moon breathing style. It will obviously be a lower priority than reclaiming my former strength, but still something to keep an eye out for nonetheless.
Izuku's three pairs of eyes wandered to the window, where he could see the buildings that occupied the skies of the downtown Mustafu area.
Putting that aside, how far in the future have I reincarnated? The scale of architecture today seems impossible compared to the Taisho period… If the engineers behind the creation of these cities have progressed so far in caliber... I wonder how masters of the sword have refined their techniques in the hundreds of years of my absence…
Izuku smiled as his eyes narrowed. It may even be that my techniques may find their equals in the swordsmen of the modern era… The prospect intrigues me…
I wonder then, what tomorrow will bring?
…
Disappointment.
Izuku found himself in front of the television watching a special on tea ceremonies when his mother changed the channel to the news. Shown on the screen was a fight between a large man with a ridiculous smile and an even larger man with features of a shark, holding bags of money.
"You see that Izuku?" whispered Inko. "That's All Might. He's the number one hero, and he protects everyone from danger with a smile. It's because of him that we can live our lives safely."
The man on screen bore muscles that far surpassed any Izuku had seen, either in this life or his previous one. However, whether or not that was to be attributed to his work ethic or his quirk remained to be seen.
Izuku was about to attempt to crawl to the remote to change the channel when he realized that a new term had been added to his vocabulary.
A hero? Thoughts of swords flashed through his mind. Is the occupation somehow related to the demon slayer corps? If that is truly the case, then the origin of these so-called quirks is becoming more mysterious by the second…
Izuku did his best to present an inquisitive face to his mother, hoping to prod her into explaining more about the occupations of heroes.
Inko smiled. "Heroes are the protectors of the weak. They defeat dangerous villains who try to harm innocent people, and save victims of disasters, no matter the cause."
Izuku's attention returned to the screen. The news switched to a program featuring up-and-coming heroes and interviewed each of them, exploring their respective quirks and what their motivations were behind their heroic pursuits. I see... it seems that the appearance of these quirks led to a forced overhaul of the criminal-justice system, leading to a profession with a status akin to an idol. Judging by this woman's reaction, heroes are universally beloved by the common folk for their role as a bulwark of the weak...
Izuku couldn't help but compare them to the demon slayers of old. If these so-called heroes are descendants of the demon slayer corps, then I cannot help but be disappointed. The slayers I knew were joined by a united desire to protect the innocent and destroy the demons. They rarely received acknowledgement of their deeds, and fewer still received them when they were alive. And yet, these heroes relish in the attention and status that the mere title of an occupation can bring.
Izuku's expression returned to a grimace. If these are the caliber of combatants of this era... then finding a worthy successor will be a tedious endeavor indeed…
…
A few weeks later, after Inko and Hisashi had fallen asleep, Izuku climbed over the railing of his crib and made his way to the phone in his mother's purse. From there he inputted the password he had seen her use dozens of times and started to familiarize himself with the digital apparatus.
The surface responds to the touch of my fingers… and responds in accordance with my input. Perhaps with this I can find a library that can inform me more of the circumstances of this new world…
When Izuku searched for the location of a nearby library, he was surprised to find the resource known as "Mikepdia", which featured a greater range of information than Izuku had seen in the entirety of his previous life.
Is this the result of someone's quirk? How do so many pages of a book fit into such a small device? He searched the site for any hint of Muzan's existence, or history of the demon slayers.
After a few minutes he leaned back. Nothing… Even though the demon slayer corps were an organization unrecognized by the government I'm still surprised to see not even a single rumor of their existence. And Muzan-sama doesn't seem to be a prominent enough figure to exist in this database either, if he exists at all…
Izuku continued to search the site for mentions of breathing techniques, known demons, familiar names, and still found nothing, and for the first time since his reincarnation, Izuku was starting to doubt his understanding of the world around him.
Why do no records exist of the Japan I knew? That could only happen if either a massive purge of historical knowledge occurred at some point in time, or if I was reincarnated in a completely different world than the one of old…
Izuku changed his focus to finding the history behind the emergence of quirks. According to the website, quirks first appeared when a glowing baby was born in China, after which multiple variations of these new "quirks" started appearing all over the world.
It is unlikely that Muzan-sama is behind a development like this.. He held no greater ambition for power or control beyond his own survival, and exposing his existence in such a half-hazard way would have yielded him no benefits… He exited the tab and started crawling back towards his crib. If neither Muzan nor the demon slayer corps ever existed, then it is unlikely that this world is the future of my old one.
Izuku's face slowly twisted into a smile.
If this world truly has no connections to my original one, then I have neither connections or reservations to hold me back.
He climbs over the railing of his crib.
This world is filled with unlimited potential.
Pulls the blanket over his body.
All for me to conquer.
Takes a deep breath.
To surpass.
And sleeps.