Just another crackfic written on my phone in sudden inspiration. Don't expect regular update.

The story happened right after Fate Stay Night : Heaven's Feel route, True Ending

Disclaimer: I don't own Fate Stay Night or My Hero Academia.

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Prologue: A (not) Heroine is born

Human, are not all equal at birth.

This is a fact that I realized when I was three years old.

Because... no matter how I think about it, clearly I am the strongest.

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A Useless Goddess

In a pure white room, Goddess Aqua lazily read another stack of paper. It was another record of how someone lived and died.

Aqua was a goddess in charge of young people who died in Japan. You might not believe it, but the amount of people who died young was big. The monotone work of guiding the lost souls took a toll on her, she was stressed and she needed an outlet.

Maybe this one would relieve her stress. She couldn't help but laugh when reading about this young man's cause of death. Maybe she could get an entertainment by teasing him, Aqua thought while taking out a snack.

With a fwoosh by her hand, she let the soul of one Satou Kazuma enter the white room.

Only, instead of a japanese teenage boy, the one appearing was a little girl with long white hair, blood red eyes, and wearing an oversized white gown with strange design, seven golden circles decorating the front of the dress. A big elaborate crown rested on her head. She also wore white stockings with matching design.

Was it in fashion for a young man to dress as a girl? And was he even Japanese? Aqua would suspect a case of mistaken identity if she didn't know the power of Heaven's System. The system had 99.99% accuracy rate.

The 0.01% error margin? That was for the improbable case of something interfering with the system. For example, if an artifact with great power that can literally grant miracles somehow screwed up soul transmigration.

Never gonna happen.

Let's not waste time and do this quickly.

"Satou Kazuma-san, welcome to the afterlife. Unfortunately, you've died. It might've been short, but your life's now over."

The little girl was confused, looking around the room with wide eyes. "Where is this place?"

Aqua repeated again with annoyance. "This is afterlife, and you are here because you have died."

The little girl then looked at the woman talking to her

In the room was an office desk and a chair, and a woman was sitting on it. The little girl examined the woman. The teenage aged woman looked beautiful, beyond what human could be.

She had long, silky smooth blue hair. She wasn't too busty nor too lacking, and had a light-purple hagoromo draped over her clothes.

"Are you the Holy Grail?" The little girl asked, feeling doubt inside her. Wasn't the Holy Grail made using her ancestor as a core? Then the manifestation supposed to appear like her, with white hair and red eyes.

The woman blinked with her blue eyes. "Excuse me? I am Goddess Aqua. I'm a goddess that guides young people who die in young age. Do you remember your cause of death? Satou Kazuma-san."

The little girl searched her left and right, and also behind her. Seeing no one, she asked the goddess, "Are you talking to me?"

"Of course I am!" Aqua half shouted. She was getting more annoyed. Not only this boy delayed the process, he was even more dimwitted than she expected. "Now I will refresh your memory about your death."

Aqua then summarized the incident. Satou Kazuma, a shut in with game addiction, left his house to buy a first limited online game. On his way back home, he tried to save a girl from being run over by a truck.

Hearing all this, the little girl only stared blankly, giving no reaction.

So Aqua continued, trying to get a reaction. The twist was, it was not a truck, but a slow moving tractor. The girl would've been fine even if Kazuma didn't do anything. He just made it worse by interfering, and as a result the schoolgirl got a fractured leg.

Worse part, Kazuma was not even run over by tractor, because it stopped before hitting anyone. He died because of shock, believing himself to be run over.

"I've been doing this for a long time, but you're the first to die in such a hilarious way!" Aqua laugh heartily.

"…" The little girl tried to hold her smile, but she was still confused. She didn't remember about any of this.

Aqua thought that the boy in front of her (with little girl appearance) was still in denial. It was normal for souls to reject the fact that they've died. So she pressed on with her mocking.

"Because of your close call with the tractor, you lost consciousness and control of your bowels, and you were sent to a nearby hospital. As the doctors and nurses were laughing and saying, 'What's with this guy, how useless–', you didn't regain consciousness and your heart failed."

"Bhuu." The little girl put up her hand to close her mouth, stopping her laughter. However, Aqua interpreted it as the boy holding his sadness and tears.

Aqua continued her merciless teasing.

"Your family reached the hospital, but before they could feel the sadness from their loss, they couldn't help but burst into laughter upon hearing your cause of death."

It was now with maximum effort that the little girl held her laughter, closing her mouth with two hands and shaking with her eyes closed.

Looking down at the little girl, Aqua thought that this dead soul was hiding his frustration. She covered her mouth and laughed.

"… Well, that ends my de-stressing session. Satou Kazuma-san, putting aside how funny your demise was, you now have two options." Aqua said.

"The first option would be reincarnating and beginning a new life; the other option would be staying in a place sort of like heaven and living the life of a retirement home."

At this time the little girl had managed to control herself and peered at the self-proclaimed goddess, scrutinizing her from top to bottom. "This doesn't look like vision from Angra..." she muttered with whisper.

"What do you mean sort of like heaven?" The little girl asked.

Aqua answered. "Heaven isn't as great as you humans would imagine. You don't need to eat after dying and won't be able to make any food naturally; there aren't any ingredients nor necessities for you to use anyway. I'm sorry if I disappointed you, but there's nothing in heaven. No television, no manga and no games. Only other people that've died before you. Moreover, since you're dead, you can't do anything kinky. You can't since you don't even have a body. The only thing you can do is bask in the sun with your predecessors and chat. Forever."

'That's perfect' thought the little girl who had been suffering for the majority of her short life. As a plus, she would be able to meet her dead parents. "Ok. I will take heaven please."

"Wait! Wait! You haven't even heard about the other option, you can reincarnate! Starting over without any memories and live again." Aqua said, a little flustered because she didn't expect this person to decide right away.

"Not interested." The little girl with white long hair said, yawning sleepily.

"Well, actually there is a third option. You can be transmigrated to a world with game element. This is great news for someone who like game like you. You can keep your memory intact, you retain your original body, and we will give you a gift such as godly weapon or powerful ability." Aqua tried to sell the third option. "The only thing you need to do there is to fight demon king. How about that?"

Well, Aqua would get a bonus for each transmigrator who took the contract to defeat demon king. With his profile, Satou Kazuma perfectly fit the type that would take this chance.

"Nope. Send me to heaven." The little girl stubbornly said. She already had enough fighting for a lifetime, why would she want to fight this demon king?

"Are you sure?" Aqua said with disbelief. Why? This didn't happen like the script she predicted. "Another life where you can have fun like in game, with overpowered weapon, isn't this the dream of every hikikomori gaming otaku?"

The little girl nodded without hesitation. "I am sure. Heaven it is."

At this point, there was nothing Aqua could do. She couldn't force the soul to do something he didn't want. "Ok, Satou Kazuma, you will be sent to Heaven. I hope you enjoy your retirement."

Aqua pushed one of the button on her desk. After this, a halo of light would come from the sky and transported the dead soul to Heaven. However, that didn't happen.

On a very, very rare occurrence, a transparent screen showed up in front of Aqua. Showing the bright letters: ERROR

"Huh? Huh?" Aqua brought up her rarely used heaven-terminal and started typing. She read the problem description. "Error 1061: Unable to process."

Aqua got more frustrated. First this person refused transmigration. Then the request to send him to Heaven was jammed for some reason. Why? Too much sin?

Maybe she would know if she checked the description of Error 1061. Meh, too much effort. She instead searched the automatic troubleshooting. The screen read:

"Proposed solution 2396. Estimated time until finished: 72 hours. Confirm? (Y/N)"

What? Three days just to send one soul to Heaven? She would be left behind by her colleagues in employee ranking! Even the monthly bonus from exceeding quota might be lost. She started to think, and then she said to the person in front of her.

"I think there is a problem. You cannot go to Heaven. Maybe you want to be transported to the game-like world instead? If you defeat the demon king, you'll receive a gift from the gods the moment you defeat him." Aqua tried to smile and persuade this person.

But Satou Kazuma still refused, with his voice that really sounds like a girl. "Nope. If I can't go to heaven then reincarnation is fine."

The little girl thought, 'Starting over with no memories was fine. Too much bad memories.' She said, "But give me nice family and good life. It would be better if they are rich."

"Hmm…" Aqua disinterestedly inputted the person's request. The moment that person refused transmigration option, Aqua had no further interest left for him. And then Aqua pushed another button.

"ERROR"

"Aaargh why is this happening again!" Aqua pushed the button on her terminal, activating the automatic troubleshooting function and pressing confirmation button without really checking the content. She only glanced at the estimated processing time, and finding it more agreeable than the 72 hours option, pressed YES."

Do not underestimate the Heaven System. It was a repository of many arcane knowledge, not limited to only one world. It searched from among multivese, finding the most appropriate solution.

Here was the screen content that Goddess Aqua didn't read:

"ERROR 1062. Unable to Process.

Do you want to search for solution? (Y/N)

AQUA: YES

Identifying problem…..

Result: Due to unknown cause, eight copies of Heroic Spirits pseudo-soul are attached to the subject soul. To be reincarnated the additional pseudo-soul must be removed or integrated completely.

Finding solution. Discovered 133 solutions. Sorted from best to worst? (Y/N)

AQUA: YES

Solution #1: Integrating the pseudo-soul with the subject soul through Class Card System from Ainsworth Holy Grail War. The subject would have power to Install or Include the heroic spirit.

Cost: The energy for this process will be converted from Dress of Heaven.

Recommended default settings (click customize to change):

Retain previous life memories, retain magic circuits, retain element and origin, retain sorcery trait, eliminating physical defect, adding knowledge about new power, lock memories until the age of three.

Inputted settings (click customize to change): Wealthy family. Loving family.

Estimated processing time: 15 minutes.

Do you want to confirm (Y/N)

AQUA: YES

Processing the Solution #1… please wait.

Aqua saw the progress bar filling slowly, but she didn't complain. It was better to wait 15 minutes than 72 hours. There were still many dead souls waiting in line, what should she do if her boss decided to cut her bonus? She wasted her time munching her snakes while occasionally saw the dead soul in front of her. The soul was in a magic circle, undergoing some kind of mysterious process.

"What are you doing to me?" The dead soul of Satou Kazuma asked, a hint of fear in his voice. Aqua really didn't know why it sounds like a little girl though. Was she unaware of things going on in mortal realm that much? She wondered why a teenage boy had the appearance and voice of a little girl.

"I am processing you for reincarnation. Just stand there and shut up." Aqua said, and took out a book. She couldn't be bothered by this dead soul but she must wait 15 minutes. Better got something to fill the time.

While she lost herself in the book, time passed, and suddenly a notification sound was heard.

DING!

Process completed. Automatically send subject to new world.

And then the magic circle flashed brightly, and when she looked again, Aqua found that it was gone, along with the dead soul.

Good, now she could resume her work.

Aqua took out the next bundle of paper and read it. And then she sent in the next dead soul.

Before her, appeared what seemed to be a teenage boy. The hair was light brown and cut short, just like common teenage boy in Japan. The clothes this person was wearing were common t-shirt and cheap jacket and long pants. All in all, he looked like an average Japanese boy, not too handsome but not ugly either.

Aqua frowned. Since when did a girl appear as a boy? Something weird must have happened in the nation of Japan. Wearing the opposite sex clothes?

Forget it, she had work to do.

"Illyasviel von Einzbern, welcome to the afterlife. Unfortunately, you've died. It might've been short, but your life's now over."

The dead soul looked confused. She was just staring blankly at Aqua.

Well, this was very normal. Humans rarely accept their death right away. She must state the facts first, and guide the soul after she accepted her death.

"You are dead because…" Aqua looked at the paper on her desk. "A battle royale between seven magicians. It said here that you do a selfless act to shut down a corrupted artifact, costing your life as a price."

The girl in front of Aqua still stared at her blankly, mouth agape. This was really hard sometimes. Maybe she still had shock from her death?

"Lets see.." Aqua shuffled the papers, trying to find out the options. She now noticed at the very last paper, written in bold:

INTERDIMENSIONAL CASE

PROBLEM #1061

RECOMMENDING QUERY TO SUPERVISOR

Must be the automated bot again. They were sometimes too paranoid and left a note like this. Aqua didn't want to call her superior for every little thing, it made her looked incompetent. She would, but only for major cases. Anyway, what was problem 1061 anyway?

She read from the paper to the girl in front of her. "Let's see, because you have a lot of hate for the world and also sin of murder, you can't directly enter heaven. Usually you go straight to hell for a while, but in this case you had done a great service to the world, so it balanced out. I recommend spending your time in purgatory fire, after that you can choose between heaven and reincarnation. Or maybe a third option, if you like."

Aqua looked at the girl, expecting an answer.

The girl (in the form of a boy) started to panic. She protested dramatically, gesticulating with her hands. "Wait! I think there is a mistake! I have never murdered someone!"

Even her voice sounds like a boy. Was it medical surgery?

"Let me refresh your memory. Matou Shinji. Remember that name?" Aqua asked lazily.

"Nope." The girl said defiantly. "Never heard that name in my life."

Aqua scowled. "Don't lie girl, the afterlife record is infallible. Every sin that you committed in life is recorded here." Aqua slammed her hand on the papers.

"I think there is a mistake here." The dead soul said. "And I am a man. Can't you see that? Don't call me girl."

Aqua crossed her arm and glared at the girl. "You are Illyasviel von Einzbern. No matter how you change your shape, your gender is clearly recorded as female. You are 19 years old, so I can call you girl."

"No wait!" The dead soul still protesting with her hands waving wildly. "I am a man! My name is Satou Kazuma!"

"…." Goddess Aqua had a cold sweat. She looked at the soul in front of her with growing terror in her eyes.

The soul continued, "I think I am dead, yeah! I saved a girl from being run over by truck! And then I must be run over instead. That's why I am dead, right?"

Aqua now had a gaping mouth, her eyes looked at the real Satou Kazuma in horror. If this was really Satou Kazuma, then who was the previous dead soul?

She hastily flipped the paper files, searching for Illyasviel von Einzbern photo. Usually, she was too lazy to inspect it, because there was really no need to know the dead souls appearance beforehand. There had never been a case of switched identities in afterlife.

There! She found on the paper files, the photo of a girl with long white hair with red eyes, identical with the previous dead soul that she had sent to reincarnation cycle.

Oh by the flaming wyrmtail! She screwed up, colossally.

Ignoring the question of Satou Kazuma, she brought up the heaven-terminal and started typing. If the soul was still in transit, she could intercept it and brought it back. If the soul had already entered the womb, she would cause miscarriage and forcefully brought it back here. The second case was illegal, but it did not matter if she didn't get caught.

And she was already past caring about legality. If her blunder was found out, she would get cut on her salary, or delayed promotion, or worse, demotion. With speed that she seldom displayed, she typed away at the keyboard, trying to track where the soul went.

ERROR

Unfortunately, the soul couldn't be tracked. It was very bizarre phenomenon.

And then, as if solving a contradiction, the paper file of Illyasviel von Einzbern on her desk burned to ashes. From the void, a new paper file about Satou Kazuma appeared.

The Heaven System repaired a contradiction. It had sent one 'Satou Kazuma' to be reincarnated, but Satou Kazuma was still in afterlife pure white room, so the reincarnation record must be mistaken. There was a record about Illyasviel von Einzbern, but the soul was not in afterlife, so it must be mistaken and must be purged.

As a result, the reincarnation record was erased, deemed as error in recording. Aqua was unable to track where the soul went.

The last data she could glimpse before it disappeared showed that the reincarnation succeeded. But the cumulative error flung the soul away somewhere to unknown universe.

Well, in a way it was convenient for her. She didn't know why it happened, she had heard of a case similar like this that happened long time ago, but the record didn't get deleted from the system. Did it mean she would be secured? As long as she kept silent, noone will find out, right?

"Heeey! Heeey, are you deaf?" Satou Kazuma still trying to talk to her.

"Shut up you useless gaming addicted hikikomori otaku! Not only your death is useless, you even cause problem for me!" Aqua angrily berated the teenage boy.

"What? What did I do?" Kazuma felt a little angry for getting treated unjustly. He didn't know anything, why would the goddess be mad at him?

Anyway, the goddess was in a bad mood, so she treated Kazuma very poorly. As a result, Kazuma retaliated to her when he was given a choice of a boon to be brought to another world, but that was another story in another light novel.

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8 Years Old

"Hmm, your child does not have any quirk." The old doctor said that sentence to my mother.

My mother, a mature beautiful woman with long black hair tied in a bun and dressed in kimono, asked for more details. "Really? So Miyu is really quirkless?""

The doctor, an old person with white beard and wearing white coat, didn't answer my mother immediately. He instead pointed to a black and white picture on the wall. "Well Madam, please look at that picture. You see, in general, a child should manifest either one of his parents' quirks or a composite of the two, by the age of four."

I also looked at the black and white pictures, depicting something similar like a foot. Later in the future I would learn that it was an x-ray photograph of foot bones.

"However," the old doctor continued, "It has to do with the presence or absence of the extra joint in the pinky toe. Humans have no need for the parts they don't use, you see. And those without the joint represent the next stage of evolution."

The old doctor then took something from his desk, another white and black picture, but smaller than the one on the wall. "Miyu here does not have the sign. She will not get any quirk." He said it with an indifferent expression.

I bet the doctor actually expected this mother and child to be sad. However, my mother just calmly replied, "Oh, well it can't be helped then. Miyu, don't be sad, quirk is not that useful."

My mother had a quirk that let her hear lower and higher frequency sound, something similar to animal ears. My father had a quirk that let him grow lost teeth. He can pull out a teeth and a new one would grow overnight. Useless, as my mother said.

Of course my mother was a little worried. A child without quirk nowadays would get ostracized or bullied by other kids. Even a useless quirk was better than having none.

But they didn't know. I had no need of quirk.

And being ostracized for being quirkless was of no issue. I didn't really care.

"But madam, why did you wait until little Miyu here is already eight years old? Usually people bring their child in the age of four." The doctor said.

"We have our reasons." My mother said with unreadable smile. After giving her farewell to the doctor, we left the clinic.

And what a reason it was. A tradition to isolate a child for seven years with her mother, practiced by my new family. I didn't know all the details, but I can see a Mystery when I was in one. Living alone with my mother surrounded by bounded field, I can't help but be suspicious. Fortunately, it was a benign power, guaranteeing my safety and health.

I wondered if that Mystery was responsible for me being quirkless. Did that mean Quirk was a disease? Or evolutionary defect?

Anyway, let me introduce myself again. My name was Illyasviel von Einzbern. After participating in Fuyuki Holy Grail War and a series of events, I got reincarnated in a new world.

My new name in this world was Sakatsuki Miyu. Sakatsuki was my family name, and Miyu was my personal name. The Sakatsuki family was an old family, tracing its lineage to thousands of years ago. It was also wealthy, owning several plot of land and business. I didn't know exactly how rich we were, but seeing the name 'Sakatsuki' at the top of skyscraper building was enough hint.

Lucky me. Oh, I actually put such request in my reincarnation. I wondered if it was alright not correcting the self-proclaimed goddess. Ah well, not my problem.

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9 Years Old

"Fear not! Why, you ask? Because I am here!"

I was watching a video that my mother gave me. It was about a pro hero hailed as the best. His name was 'All Might'.

This was actually for history class homework. We should write an essay about one hero, preferably someone debuted more than five years ago. Of course, my mother pointed to the most popular hero.

My friends and everyone else said he was cool. But to me, his performance fell flat.

True, he did a good job rescuing people and defeating villains. He also had the right attitude for a hero. But I can't help but compare him to other real heroes.

Heroes that I can Install.

Not that I had tried it. The knowledge was there in my mind, and I had my circuits supplying the prana. But because of my age, I was under constant supervision. How can I explain to my parents if they saw me doing ancient hero cosplay in the house? Even activating my magic circuits involved a lot of hiding.

The heroes I can install were:

Saber – Arturia Pendragon

Archer – EMIYA

Archer - Gilgamesh

Lancer – Cu Chulainn

Caster – Medea of Colchis

Assassin – Hassan of Cursed Arm

Berserker – Heracles

Avenger – Angra Mainyu

Anyway, I guessed this meant that Rider was alive. I assumed she remained with Sakura. I vaguely remembered about different Assassin guarding the temple gate, but I had no idea what happened to him.

My favorite Servant was Berserker, but even I can deduct that trying to Install him would result in mental pollution.

I had my magecraft, and it was still as strong as my previous life. If I live my life peacefully, the chance that I would need to use my Install ability was low. I planned to enjoy my second chance at life, living peacefully in the care of my new family.

I was still an only child, but I was sure another little brother or sister would be born. Then I would be called Onee-chan!

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10 Years Old

A group of superpower villains attack my elementary school, taking everyone hostage.

Could you people not ruining my life's plan?

=====end=====

AN

1. The goddess Aqua and Kazuma came from light novel/ anime Konosuba.

Basically, because of mixup mistake, Illya from FSN changed position with Kazuma.

2. Rider still left alive in FSN HF True Ending, so her soul is not included here.

Gilgamesh and Heracles would have mental pollution effect when installed

3. Illya reincarnated in MHA world and bring along her magecraft and ability to install Servants. She had no quirk. But she had Sakatsuki family body constitution, giving near infinite mana.

She became Miyu Sakatsuki. Basically they were the equivalent of each other, so one reincarnating as the other is plausible.

4. Yup, overpowered much, I know.

Tell me what you think in review.