Use The Returner Quirk

Disclaimer: The characters and storyline of [Mass Effect] and [My Hero Academia] don't belong to me, they belong to their respective authors/companies. This is a fictional story created solely for the purpose of entertainment, and it's not for profit.

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Note 1: In this story the U.A. is a university, and the age of the characters is 17~18 years old and up. The age has been changed since it is a crossover with mass effect and in every mass effect crossover there must be 'completed romance' or it would not be a crossover with mass-effect perse (you Know)... So I consider it inappropriate to use characters that are 14~16 years old in a story where there is this kind of romance. The romance will be well grounded and developed, I'll do my best.

Note 2: Don't forget to click the "favorite" box to support the story. A review is also appreciated in advance, if you are interested in leaving your opinion about it. And, after the library section, which you will find at the end of the chapter, I left a message in which I wrote a little more about what this story will be about. Check it out if this chapter caught your attention.

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Prologue: The Awakening

Mission 01: Use The Returner Quirk

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Final Note: Sometimes, in the undubbed version of MHA, the characters use the word "KOSEI" (Here it's written in Western characters) instead of quirk. Kosei is a Japanese word meaning "Individuality". Therefore, kosei is a synonym for quirk. Sometimes, I will use kosei to refer to a quirk/quirks to avoid abusing the latter word.

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"Don't let them control you!"

"I tried. Shepard."

*Bang!* The illusive man was finally dead. A bullet from a Carnifex ripped through his skull, corrupted by alien technology, and entered the only thing about him that was still human. His brain. It was a fitting end for the bastard, who at least had the decency to kill himself after all he had done under the Reapers' control.

Shepard only wished that the bastard had suffered more, but that involved time that neither he or Anderson had at the moment. Warm blood dripped from practically every pore on his body, just like Anderson's. He could barely stand upright.

-o-o-o-o

Minutes passed and Anderson died. His loss was one of the most painful things he ever experienced. Although his life had never been easy, he never expected to feel so much sadness at a time like this.

But he didn't have much time for regrets because the wave of pain didn't stop trying to slow him. The Citadel's device wasn't working, which left him with feelings of frustration and agony that would have collapsed any other biological being. But not him, not at that moment, not in that place and not while he was still alive. He kept fighting, it has been the only thing he knows how to do since he 'woke up' in this world.

He pressed buttons and kicked the console until something finally happened. He didn't know if he really achieved it by his own merit, if it was a coincidence or if someone had just been playing with him all that time. The only thing he knew was that he was taken to a new section of the Citadel and then he could see an internal section of the Crysol and the 'boy' who was guarding the place, whose holographic appearance was almost identical to that of the child he was unable to save.

That was incredibly strange...

"Your time is coming to an end. You must make a decision."

But the words of the child were even more strange and heartbreaking. For three years he had dreamed of destroying those sons of bitches who had brought so much pain to countless planets and living beings in countless cycles of creation and destruction. But now this child had just told him that the destruction of his archenemies would also bring the destruction of his synthetic friends and his entire 'lineage'.

Upon hearing that, even though he hated the Reapers and their targets with every fiber of his being, he couldn't do that to EDI and make Legion's sacrifice be in vain. The Geth had earned a chance to prove that they deserved to live and be free. Everything they had fought for was going to be lost if he destroyed those bastards.

The synthetics he knew were very different from the Reapers: they had feelings, dreams, desires and wanted to peacefully cooperate with organic beings. Even if they had not been born through an egg or birth, he knew they were alive.

But more importantly, he knew that synthetics and organics could come to understand each other! He, Legion, the Geth, EDI, Joker, Tali, Glyph, and the rest... They had all proven that it was possible!

He made his decision. It was incredibly difficult but he made it after his analysis came to a resolution. He ignored the red light and the green light, and then turned to the blue light.

Destroying the Reapers was no longer an option. And the last option that the 'Starchild' had proposed to him seemed too suspicious or fanciful; if what the boy said was possible, what would prevent the Reapers from controlling the will of new techno-organic beings 'born' in the Galaxy?

So, before his life came to an end because of the deadly injuries to his body, he decided that before he took his last breath a copy of his consciousness would force the Reapers to obey his will for all eternity.

He would have liked it if there was another option that could make everyone happy, and one that would have allowed him to continue living to be by the side of the people he loved, but life seemed to have decided to screw him over one last time.

"Let's end this. Once and for all." With a completely tired and annoyed face, he said those words and walked agonizingly towards his destination.

-o-o-o-o

Before touching those cranks charged with powerful electric currents, he took a deep breath.

Then, with a palm pressed to the cranks, the horrifying pain spread through every fiber of his being but he forced himself not to scream. He would not grant the Reapers that satisfaction, at least his organic body would not give them that before it disappeared.

As the pain continued to expand and as his body was vaporized, he thought one last time of the loved ones he left or would leave behind in this world.

Anderson. Thane. Mordin. His beloved Liara. And all his dear friends.

At the thought of them, the pain finally disappeared.

A moment later, as that comforting smile took over his expression, the freckled and green haired commander, Zuku Shepard, had finally ceased to exist. The legend of the greatest hero in this galaxy had come to an end.

-o-o-o-o

But where one legend dies, another will always be born.

-o-o-o-o

Inko Midoriya watched as her son laid on the bed in his room, with the heart monitor beside him still releasing the soft sounds of his heartbeat. She was gently stroking his hair.

"Oh my baby, my poor baby," Inko murmured "You've already been asleep for 3 months. It's too much now... I can't bear this pain anymore... Come back to me please, my dear Izuku. Fight. Please, my baby, fight and come back to your mother."

Three months ago, just after his 17th birthday, Izuku Midoriya had been hit by a moving van while walking to school, and had been in a coma ever since. Doctors were unable to wake him up even after the green haired man's body was healed, so he remained unconscious and sleeping peacefully in a certain hospital room, until he was moved to his room in the apartment that was his home when hospital costs became exorbitant.

With Izuku's father having passed away quite some time ago, Inko was forced to take out a large loan to pay for the treatment and hospital equipment needed to continue treating and monitoring her son's health at home. Two months and 19 days had already passed since that move.

She had tried everything to bring her son back; she got doctors and other professionals with various quirks to treat her son, from psychics who read his mind and tried to wake him up, to healers with all kinds of various healing powers. And despite all of the above, Izuku remained in a coma.

Inko's current routine consisted of the following: she checked her son's condition every day, then washed his body, delivered nutrients to the IVs connected to his forearms, changed his underwear, threw away his waste, shaved his head, massaged his muscles in the hope that they would not show any signs of atrophy, and regularly moved his position to prevent pressure ulcers from forming. She always kept an eye on the heart and brainwave monitors, hoping that someday she would see some change in her son's condition.

*Beep* Thankfully, on this occasion, her tears would finally have an answer as a soft beep interrupted the steady tone of the heart monitor, causing Inko to blink in bewilderment as she looked at the screen of the monitor.

Two spikes on the screen that measured brain waves manifested themselves. And then there were more and more peaks and beeps, until the machines suddenly stopped releasing unsynchronized and annoying sounds as they exploded after they were filled with a powerful electric current, which traveled in an instant from her son's body to the devices.

"NOOOO!"...At the sight of that scene, Inko shrieked in horror, thinking the worst. But...

"Uh?"

As she turned her head and focused her eyes on her son's head, she finally realized that her offspring's bright emerald eyes had opened for the first time in two and a half months.

The two looked at each other in silence for a moment in shock and awe. The corners of both of their eyes filled with water in no time and just as the tears began to flow. Inko reached over and ran her hand gingerly over the green haired young man's cheek. She was so lost in her happiness that she didn't notice the scars that now adorned her son's left cheek and part of his forehead.

"Mother," Izuku said, almost in a whisper, he didn't want to be disappointed again. His strong desire to see her again had caused his brain to create mirages of her figure in the past. He had probably already thought a long time ago that he would never see her again. "I missed you. You don't know how much I missed you."

-o-o-o-o

A week after he woke up, once the curtain of night descended on the day, Izuku stared at the ceiling of his room and ran the events of the last 7 days through in his mind.

He had spent an entire day trying to comfort his mother, who spent most of it sobbing with relief and happiness in his arms as they sat on the couch in his apartment, where they caught up in no time.

Later, when she noticed the scars on her son's face, she wasted no time and took him with great distress to the hospital, where the doctors who initially attended him were.

There, his brain waves were examined along with his other bodily functions through various medical machines and blood tests.

Afterwards, he had to undergo a series of physical and mental tests while the doctors checked to see if the accident, and subsequent coma had changed anything else.

Oh, and the coma had changed something else. In fact, it changed many things. The doctors, his mother, and even he couldn't help but be surprised by that fact. Not only was he now approximately 1.87m, but the performance tests initially proved that what he had experienced in that other world had not been a hallucination caused by his dying brain or something like that.

Not only did he perform so well in every physical or mental test that he almost looked like a soldier who had been put on the Captain America serum, but in addition to the superhuman physical and intellectual abilities (that almost seemed like a kosei itself) he now also truly possessed a quirk. A supernatural power that at first he dismissed as something else, as he had thought that there was no chance of it being a quirk, even if he was also able to observe its effects in this world, but ironically the doctors confirmed even with blood tests, what he refused to believe.

Not only had all the experience, will, memories, muscle memory, knowledge, physical strength, and reflexes he had acquired as Zuku Shepard appeared as if by magic in his body and mind right after he woke up from his coma, but something else had also accompanied him from that other world.

"This is completely absurd! It doesn't make any sense!" Enunciating with great annoyance and a bit of sarcasm, Izuku flexed his hands, watching his muscles tighten and twitch beneath his skin. He still felt as strong as he did in the other world. No, even a 'little' stronger, physically speaking.

"Shockwave." Thinking of the ability and saying it out loud, he raised a hand and pointed it in the direction of a collection of toys resting on one of his desks.

Moments later, he let the force he felt accumulated in his nerves flow and then all the action figures were sent flying as the wooden shelf fractured into a thousand pieces by some kind of energy in the form of green waves.

Upon awakening from his coma, Izuku never stopped feeling the pulse of his biotics through his nervous system, veins and tissues. The supernatural power that he had spent years training, cultivating and enhancing was still there. Although, he felt that his ability to use that power within himself had unfortunately returned to its beginnings, as if he could no longer release or control the true force that his biotics were capable of exerting in his previous life.

This revelation made him feel more attached to his supernatural power, as if it were more a part of him than it had been in that other world. So he very much doubted that these biotic related powers were working with element zero or biotic implants, as the mass effect waves were not supposed to have a green color. However, the tomography and magnetic resonance scans that the doctors took of him revealed that his nervous system still possessed the organic nodes that made him the second known case (after Subject Zero) of a natural biotic born into the human race in that dimension.

So he had been mistaken in thinking that his biotic powers no longer depended on element zero. Either that, or the nodules in his nervous system had undergone some kind of unknown change that caused his mass effect waves to be green.

But, whatever the case, most likely due to this change his biotics underwent, he was now unable to use the mass effect fields at full strength. Somehow his biotics had become a quirk in this universe, and like almost all quirks that awaken in this world, it had to be trained and mastered for it to reach its true potential.

"Hehehehe." Izuku laughed. And once again, he smiled proudly as he saw the accomplishments of his recent action.

All his first life he searched for some way in which he could become a hero; he tried to awaken his quirk for years without reaching any success, until a little over 3 months ago. Apparently, he had finally gotten a way to achieve the most desired goal of his first life.

Nostalgia soon caught up with him as he looked at the All Might figures now lying on the floor; how long had it been since the days when he was an innocent child and a fan of the heroes?

"How am I supposed to explain everything that happened to me? Am I supposed to tell them that I woke up in the body of my other self in an alternate earth of another universe? One where there were also strange powers born of quirks that respected the laws of physics? That I was in a world full of incredibly advanced technology? How are they supposed to believe that I spent over 30 years of my other life fighting aliens and monsters born of bioengineering and technology so advanced that most science fiction tales on this planet fall short?...Yes, I'll definitely just let them believe that my physical condition is also due to the awakening of my quirk, the Mass Effect. And I'll 'bury' the rest deep in the back of my mind."

Saying that an errant thought wiped the smile from his lips, making him frown as his eyes watered.

As he evoked certain memories he also sighed with great sorrow. He recalled all that he had lost or abandoned after leaving that universe. The incredible worlds and landscapes he had visited, the achievements he had made, the people he had saved, the companions he had met, the friends he had made, and of course, the woman he had fallen in love with.

In that place, he had experienced another life very different from the one he had had as a quirkless in this world. He still remembers the first memories he has of that other universe are quite bitter because after waking up in the body of a 4 year old boy (whose appearance was identical to the one he had at that age) he realized that he was a laboratory rat and a homeless, and orphaned child, whose only belongings were worn out clothes and a metal necklace which carried a small silver plaque with the following information engraved on its center: "Shepard/Blood Type O Negative". To this day he still doesn't know if "Shepard" was his last name or his first in that world.

In any case, he had memories of the streets of a certain big metropolis in that alternate Earth where he was 'raised', and in order to survive in that hostile environment he was forced to abandon the morality he had built in his universe of origin.

His childhood was filled with petty crime and gangs, which allowed him to stay safe and not starve to death. That was until he decided to enlist in the Alliance army when he turned eighteen.

Although he had become a delinquent who stole all kinds of items to survive and gave part of his profits to poor people to help them survive too, like a futuristic Robin Hood, and sometimes killed gang members who deserved it, he always kept the dream of being a hero in one way or another.

He thought that enlisting in the army would at least allow him to save other people. And after a few years, his career in the army became so epic, that he barely has words to describe all that he had lived as a cadet, a soldier, a sergeant, a lieutenant, and a lieutenant commander. A commander who at the young age of 33, had achieved the impossible: uniting an entire galaxy against a common enemy. An enemy so incredibly dark and powerful that it had caused untold death and destruction for hundreds of millions of years.

And in the first hours after he had returned to his home universe, he tried to delude himself into thinking that what he had lived had been just an incredibly realistic hallucination or lucid dream.

But unfortunately, he couldn't live in denial for long: he knew that there was no way his imagination or mind had the capacity to create such a detailed and realistic 'dream world'. The subsequent evidence that he retained on his body was the undeniable fact that somehow, the supposed quirk he had been told he possessed since he was tested at age 5, was some kind of ability that exercised the powers of a 'Returner' archetype character from classic Japanese tales. Someone who has traveled/been reborn in another world, gained attributes or powers, and returned to their own world, usually keeping those powers intact and at other times obtaining variations of these powers and abilities, adjusted to the physics and logic of their reality of origin.

Probably, his quirk had finally activated at the moment of his accident and had sent him to be 'reborn' in another world to later bring him back together with all the attributes gained in that other place. Of course, his kosei gave him all of the above.

After his purpose in that other world was fulfilled and after his other self died, or at least that was one of the possibilities his mind conjured up after trying to make sense of what had happened to him in that other reality, and what was happening to him in his universe of origin.

Another possibility that he also thought of, besides believing that maybe he was still in a coma or that he had already gone completely crazy, was that maybe his quirk was really just some power that enhanced his physical strength and reflexes to a superhuman range. And that, in reality, the scars on his face and body plus the biotic abilities and the omnitool on his left arm were the result of the blatant and cruel prank of some kind of divine entity who was too bored and too lazy and bitchy son of a bitch to show up and explain his game plan to the rejuvenated green haired man.

After a few minutes spent in contemplation, he once again sighed heavily as he stood up. Feeling sorry for himself and what he had lost was not going to bring back the things he loved from his former life. And if he learned anything very well from that life, it's that the only way to endure pain and to move forward, is to stand up and keep fighting. Value and remember the valuable things from the past, learn from them, but don't get stuck in the past or you will break. Keep moving forward and keep fighting until you create a change in yourself, or in the world around you. Keep fighting… That was the only way he knew. It was his mantra.

After several minutes of repeating those words to himself, when he finished dressing in sports clothes, he decided to leave his house. He inhibited the melancholic thoughts of his soul, and for his mental health he forced himself to continue forward. He forced himself to build a new future for himself and for his mother in this universe. So he had to restart his first life again; he decided to restart the path to those dreams he once had in this world, and at the same time he set out to make the necessary changes that his first life greatly needed.

-o-o-o-o

"Well, this seems to be on the right track," Izuku muttered as he stretched his muscles. He was currently standing on a shore of Dagobah beach, looking at the remaining trash that covered the sand of this place, though only 2/3 of the junk that had turned this place into a dump remained.

"Just as I thought, it's turning into a good exercise routine." At once, he flexed his arms in front and then placed his hands on either side of a broken refrigerator.

Less than a minute later, and with some difficulty, the refrigerator was finally crushed by those strong hands and turned into a piece of scrap metal resembling an imperfect ball of metal as the green haired man molded it into something that could be carried more easily. He still felt as strong as in the other world, although strangely, that physical strength that he had managed to cultivate with hard work and dedication in his military training was reflected in this universe in a slightly stronger way than he remembered.

Strangely, some of the combat stats he retained as Shepard, such as his physical strength, in his home universe seemed to behave in a different way compared to the other plane of existence. He was probably now as physically strong and durable as a Yahg, or perhaps even stronger. He certainly felt that the walls of a building would suffer if he threw a punch at them.

When he realized the changes in his physical strength, he analyzed that perhaps it was due to the fact that the laws of genetics in the human beings of his reality of origin had characteristics even stranger than that of the biological beings of the other plane of existence. After all, in his original universe the genome of his species could give rise to powers as strange as the biotics, or even stranger powers than those for they could alter the laws of physics, chemistry, thermodynamics, and otherwise to a great extent.

And there were also superhuman beings, whose bodies had been refined by their quirks to such a degree that they seemed to have a second or third quirk in addition to the one they already had, even though the other components of their body didn't possess supernatural power at all.

For example, he had seen how the arms and hands of that guy he claimed was his friend, had become so strong as to withstand those terrible explosions, and it was likely that the rest of his body was also able to withstand the shockwaves of his own quirk, which shouldn't make any sense given that the other components of that body were completely human. However, due to that lack of common sense in the genome of the humans of his universe, it was very likely that a human being without a quirk, could go on to develop superhuman attributes if they demanded their body to go above and beyond with a crazy and risky exercise routine.

"If only I had known that I could be a hero with just an exercise routine as absurd as the N7 training, I would have started training since..." Izuku sighed in frustration, but seconds later shrugged his shoulders. "Meh, it's not worth thinking about that anymore."

He quickly abandoned that line of thought when he recognized that he couldn't change the past, so he decided to continue with the training of his body and quirk.

He then hit with the green energy spheres that came out of his hands, three pieces of semi spherical metal scrap that he had created by manually bending scrap that were near him.

After they were wrapped in a green aura, they levitated at ground level. With that done, he charged those objects with great ease and ran 3km towards a large trash can as fast as he could before his biotic skill, [Lift], stopped taking effect on the objects.

Twenty seconds later, a washing machine and 3 decomposed, and manually compressed refrigerators were correctly deposited into the industrial trash can.

"[Lift] still behaves in the same way as on the other plane of existence. It generates a sphere of energy that reduces the mass of whatever it touches. So it will reduce the weight and even make objects, allies, friends, enemies and other things levitate, as long as the sphere touches them. Hmmmmmm. However, it seems that the levitation range has weakened and so far I haven't been able to strengthen it. My body and mind don't seem to respond to my desires and I'm still unable to deposit all that energy inside me. It also seems that my stamina drains a little every time I form a sphere and I'm starting to feel a headache and muscle aches… How strange... Hmmmmm. Is there another way to deposit that energy into the sphere I form? Or is my inability to make the effect of this sphere stronger due to my lack of training with this quirk? Or should I just make my body and my quirk even stronger and then imagine a more powerful sphere? The Mass Effect quirk will have other limitations or variations in this world compared to the biotics of that other universe?..." A verbiage of information was enunciated with great mental processing.

After a minute passed, Izuku sighed wearily and stopped overthinking things. "Aaaaah, too little information. I can only continue exploring the characteristics and scope of my powers."

Having settled on that, the green haired young man sighed in defeat and set out to continue his training with clear goals in mind: he wanted to completely master his kosei Mass Effect (or biotics for short), and at the same time he wanted to push the strengths of his body and mind to the limit.

He wasn't someone power hungry like the Illusive Man, but if he could keep improving himself he was going to try. All with the goal of becoming an all round hero, ready for any kind of situation. Not for nothing, as he had trained in that alternate earth as a Sentinel; a biotic soldier who also knew enough about technology and engineering to use it on the battlefield by utilizing a diverse amount of technological talents that favored him.

*Crash!*

A few minutes later, metal screeched loudly on the beach as a car collapsed in on itself due to the heavy punches of the boy, who most likely wanted to turn the old and broken down car into a compressed ball of scrap metal.

In no time, fragments of metal were scattered across the sand and Izuku's smile grew very wide. He knew he would be ready for the U.A. entrance exam, but would this exam be ready to meet Commander Shepard?

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To be continued...

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Library:

(Section created to solve doubts and/or place skills revealed in the chapter and/or some other information of the characters shown in the story. Read the following keeping in mind the voice of BKNHA's quirks presenter)

Returner!: The kosei always possessed by Izuku Midoriya, awakened at the moment he suffered a terrible accident. It exercises the powers of a "Returner-type Isekai character" in a limited way. When the user of this quirk falls into a coma or suffers an accident that makes them sleep for more than 48 hours, 'Returner' will send the consciousness of their master to an alternate universe chosen at random as long as a variant of the Returner' user exists in that universe. If a variant exists in that other dimension, that variant will be possessed by the Returner consciousness/user, who will be able to live a second life in that other world, if desired.

The moment the quirk considers that its user has fulfilled its purpose or when every neuron in the possessed body dies absolutely, 'Returner' will return its user's consciousness to its home universe and alter the cellular and molecular structure of its user to give it all the 'bodily' attributes it has cultivated in that other world. The biological powers obtained will be modified in a quirk, while those things that don't possess a link to the DNA or biology of their user, such as purely technological implants, will be converted in the same manner in which they were used or obtained, while retaining all stored information.

Since the laws governing the quirk world are obviously different from the 'transfer world', the physical attributes obtained, such as physical strength/durability/stamina/speed/reaction speed/reflexes/sense acuity, will behave differently in the quirk world. But even though all of the above probably makes this quirk the most powerful quirk in technical terms, the following limitations must be taken into account:

First; if the user dies in their home universe, it will be impossible to bring their consciousness back from the world to which they were transferred, so they will be trapped forever in that place.

Second; the quirk modifies itself to be able to grant to its master the powers/attributes that they cultivate in that other plane of existence. So after this modification occurs, "Returner" will no longer possess the ability to send the consciousness of its user to another world if they become comatose again and/or if they sleep for more than 48 hours after suffering an accident.

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Editing note 08/13/2023: This chapter has been reviewed and edited by a beta reader. Please let me know your thinks about the grammar and wording.

Best regards.