Chapter One: Despite How This Story Begins, It's Actually Crack

Twenty-year-old Izuku Midoriya stared at a map of Japan and tried to focus. The red lines on the map showed how far the decay had spread. Tomura Shigaraki had currently destroyed half of Japan. Izuku had been there when Musutafu had crumbled to nothing. He'd lost his hand and he hadn't been able to save a single person.

His vision blurred. Tears formed in his eyes. He wiped them with his sleeve, careful not to let his hook hand touch his face. After the destruction of Japan's economic structure, he hadn't been able to obtain a more realistic prosthetic.

The grey areas on the map indicated the territory of All for One. Most of surviving Japan had submitted to him, even though he'd been responsible for this whole tragedy to begin with. Not that people knew that, in all fairness. Tomura had long ago slipped his former master's control and now sought to annihilate the whole world. All for One was one of the few people left who could fight the insane monster his former protegee had become. Civilians hailed the villain as the only one left who could protect them. After all, hero society had failed them.

Izuku's stomach growled. It had been a long time since he'd eaten, and his last meal had been a few mushrooms forged from the forest surrounding the camp.

His mother was dead. All Might was dead. His former teachers were dead. All of class 1-A was dead. The only survivor of class 1-B was Neito Monoma, who was outside forging for food to feed the ragged population of civilians they'd taken under their protection. To give the blonde credit, he'd matured immensely since becoming one of the only two surviving heroes in Japan.

Izuku wondered what the hell right he had to live when he didn't have the slightest clue how to save anyone.

The First One for All User appeared before him, his image wispy and his white hair glowing. "I recognize that look in your eyes, Izuku. Stop blaming yourself. There was nothing you could have done against Quirk Singularity."

"I could have stopped Dr. Garaki," Izuku mumbled.

Dr. Garaki had released something into the air in order to cause his beloved Quirk Singularity event to happen faster. No one knew exactly what he'd done, because the mad scientist had died shortly afterward. But it had caused Tomura's decay to evolve into something capable of consuming all of Japan. The League of Villains had been the first to die after their leader's quirk spun out of his control, and the despair had driven Tomura completely insane. Izuku had given up on his naïve desire to save the villain thousands of deaths ago.

Countless people around the world had died instantly as their quirks ran amok. Izuku could no longer use One for All. It had gotten so strong that to even swing a punch would disintegrate his body, much less to access one of the other quirks inside it.

As a side effect of One for All's increasing power, the previous users had become able to speak to Izuku even while he was awake. They'd helped him find food, track down survivors, and avoid Tomura's rampage. All Might had given him one last insubstantial hug and told him how proud he felt of his successor. Unfortunately, mere ghosts could do little more.

The First said, "I didn't come here to listen to you torment yourself. I came to tell you that we still have one final option. There might be a way to end this."

Izuku's head shot up. "I'll do anything."

"It will be dangerous." The First bit his lip. "It's more likely to kill you than save the world."

Izuku laughed bitterly. "Do you think I care at this point? All for One has placed an enormous bounty on my head. He has all his people hunting me with orders to take me alive. I'm putting everyone in this camp at risk. Before you arrived, I was planning my escape route for when I sneak out tonight. I know I can't survive on my own, but I can't take the few survivors down with me either. All for One will probably capture me and torture One for All out of me."

The First looked uncomfortable. "I don't think that's why he's looking for you…it's not exactly death you need to be afraid of…I've been trying to figure out how to tell you this…"

"I don't care," Izuku interrupted. "I don't want to be alive when all my loved ones are dead. Tell me your final option."

"One of the previous users had a time-travel quirk. It only reversed time a few seconds, but that was enough to be useful in fights. Now that our power has spun out of control, we believe we might be able to return you much further back in time."

"Then I could save everyone…" Izuku whispered. "I'll do it." He raised his hook-hand to stop the ghost from speaking another word. "I know this could kill me. I still feel twinges of pain from what happened to my body the last time I tried to use One for All. I told you, I don't care. I'm going to do it."

"We don't even know if this will work. The power has gotten so strong, it might overshoot and wipe you out of existence like Eri—" The First stopped. Neither of them wanted to remember what had happened when Quirk Singularity had hit Eri. Against her own will, she'd rewound Aizawa from existence. In the space of a minute, she'd killed the closest ten thousand people to her. Then she'd grabbed a kitchen knife and slit her own throat before she could hurt anyone else.

Izuku had a lot of nightmares. One of his top ten came from the memory of Eri telling him that he never should have saved a monster like her right before she killed herself. The vestiges had managed to protect him from being destroyed by her, while he'd stood frozen, unable to stop her from plunging the knife into her throat when he knew full well people were dying by the thousands the longer she lived. His inaction still haunted him. An angry mob had chased him out of Musutafu because they blamed anyone with the faintest connection to her. Ironically, that was the only reason he'd survived the city's later destruction.

Standing as tall as he could with his spine injuries, Izuku said, "Let's not waste any more time. You know I'm going to try, no matter the risk. Give me the quirk."

The First smiled sadly. "I know, and I respect you for it. It's been an honor to have you as our Nineth wielder, Izuku Midoriya." A distant, melancholy look filled his eyes. "I wish I'd told you this sooner: my name is Yuuto Shigaraki."

"It's not Yoichi?" Izuku asked, confused as he clearly remembered hearing the Second call First that.

"I changed my name after becoming a professional hero…changed it a couple times during my exciting days on the run, actually. But I want you to know my real name." He held out his hand. "Thank you for deciding to save the world."

"Thank you for giving me the chance." Izuku shook the glowing hand. His world exploded with white light as the time-travel quirk consumed him.

Izuku opened his eyes.

He still had eyes. He would call that a good sign. The ceiling overhead looked white. Softness shifted under his back as he tried to sit up.

His forehead bounced off glass. He lay in some sort of capsule. It reminded him of a sleeping pod from a science fiction movie. His arms clearly belonged to an adult, not a child. An IV had fallen out of one thin wrist.

Izuku felt a twinge of panic. If he hadn't gone back far enough in time, to his childhood, then he wouldn't be able to save anyone. Yet he didn't remember anything like this from his recent memory. It had been over a year since Japan had surviving medical facilities for anyone to use.

He glimpsed his own reflection in the glass overhead. Though blurry, he could make out the straight white hair, delicate features, and green eyes of the First One for All User.

The air smelled dusty. Izuku's nose twitched. The nose of the First twitched, too.

Realization dawned. Izuku screamed.

Alarms blared in response. Red lights flashed overhead. Izuku recoiled from the sudden sound and noise. His head throbbed, and his body felt weak as a kitten's.

Not his body. Somehow, he'd ended up in the body of the First.

The glass pulled back. White mist rose out of the capsule. A head with white curly hair and freckles peered down at him. His long-absentee father, Hisashi Midoriya.

This was when Izuku decided that he must be dreaming or insane.

"Yuuto! You're awake!" Hisashi stared at him like a man wandering in a desert who'd found an oasis. His face broke out into the biggest smile. "After so many years…decades…you finally woke up. I'm so glad." Nearly sobbing, he gathered Izuku into a hug.

Izuku's brain short-circuited. He twitched. "D-dad?"

"Surely I don't look all that much like our father? I thought I'd aged well." Hisashi took him by the shoulders and looked him in the eye. "It's Hisashi, your older brother."

"What the hell?" Izuku's lungs seized. He coughed and spat out blood.

"Breathe deeply." Hisashi rubbed circles on his back. "There, there. You're safe now, little brother."

Brain neurons fired, making connections. Hisashi had called him "Yuuto." Yuuto was the First's birth name, a name quite likely only he and his older brother knew since even the other One for All users had addressed the First by his changed name. Hisashi had just referred to him as "little brother." Hisashi Midoriya was All for One. His father was All for One.

Was that what the First had been trying to tell him about why All for One wanted him alive? Izuku had a sudden urge to wring a ghost's neck. This seemed like valuable information he'd needed to know given his mission involved stopping All for One! His head spun, unable to keep up with so many dizzying revelations.

His stomach growled.

Hisashi leapt up. "I'll get you some food, little brother. Stay here." His eyes shifted to wariness. As that shadowed gaze tracked his every movement, Izuku could almost see Hisashi trying to decide if he should restrain him. Cautiously, Hisashi asked, "Do you know who I am? How much do you remember?"

Izuku reached a split-second decision.

The First One for All User's body must have been kept in stasis by All for One ever since their ancient fight. No matter how happy Hisashi might be see his brother, he remained a prisoner here. If he was revealed as an imposter, then Hisashi would become a lot less happy to see him. The "I'm your son from the future" story wouldn't be very convincing. Better to pretend to be the real Yuuto. In which case, he'd better pretend to have amnesia.

Widening his eyes helplessly, Izuku said, "I'm sorry, I don't know who you are. I don't know who I am, either."

Triumph flashed in Hisashi's eyes. Almost too fast to be seen, but Izuku had been watching for it.

Hisashi ruffled his hair. "Your name is Yuuto Shigaraki. I'm your older brother, Hisashi. Don't worry about anything. I'm going to look after you from now on."

As he'd hoped, Hisashi left without restraining him. Izuku knew he couldn't escape at the moment—his body felt so weak he could barely walk, and Hisashi would definitely still have his guard up. But as long as Hisashi kept pretending he wasn't a prisoner, he'd have more opportunities to run or attack. He just needed to keep up the act to prevent his father—to prevent All for One from getting suspicious.

It wouldn't be hard to act weak at the moment. Izuku had to lie down or he might faint. The ceiling swam. He coughed some more.

Hisashi returned moments later with a bowl of soup. "Say ahhh!"

In horror, Izuku realized that his father expected to feed him.

How would the real Yuuto react to this? Based on his stubborn personality, likely he'd demand to feed himself. Izuku shared the same inclination. But was it wise to start a fight so early? On the other hand, would it look suspicious if he didn't argue?

Trying for a middle ground, Izuku said, "It's kind of you to offer, but I can feed my—"

His words were cut off as a spoon was shoved into his mouth.

The simple chicken soup tasted like the best thing he'd eaten in his life. Not only was this body famished, Izuku had been surviving on mushrooms and canned goods for years. Warm food tasted heavenly.

Without thinking, he opened his mouth for more.

The soup vanished in short order. Looking extremely pleased, Hisashi said, "I doubt your body can handle solids at the moment. Try to recover, then you'll be able to eat better food. Now, it's time for a medical examination."

"Wait. I have questions." His father's face was still intact, but that only gave him a rough idea of the time period. Needless to say, he needed to narrow down the date in order to save the world. "What year is it? Where am I? And how did I end up in a coma?" The last question, Izuku could already guess the answer to—probably during the first fight between One for All and All for One. But it might look suspicious if he didn't ask.

"You're in Musutafu," Hisashi said, then named the date and year. Izuku breathed a sigh of relief. Almost exactly when he'd been aiming for. It was just a pity he'd ended up in the wrong body.

Hisashi took a moment to answer the last question. "You were in a car accident, little brother."

"A car accident. What happened?" It took all of Izuku's acting ability to sound curious rather than sarcastic.

"A drunk driver rear-ended you. Very tragic."

"You said something about me being asleep for decades…"

"Did I? I must have meant that it felt like decades." Hisashi smiled brightly. "You can't possibly have been asleep that long. We're a perfectly normal family, not a bunch of immortals. Ha-ha."

So that was how he planned to play it, huh? This suited Izuku's purposes as well. "Of course not. That would be silly. So what do you do for a living, big brother?" Boy, did that address ever feel strange on his tongue.

But being called that made Hisashi's whole face light up. "I'm a very respected businessman."

"What did I do?"

"Oh, you were far too sick to work. Too sick to leave the house, really. Your lungs can't handle outdoor air. Luckily, you had your wonderful older brother to look after you."

It was all Izuku could do not to snort. He was expected to swallow such blatant lies? Apparently, yes. Can't go outside, seriously? His father was a controlling dick, and clearly Izuku had been lucky to avoid him for most of his previous life. "Do we have any other family?"

"We lost our parents a long time ago. I have a wife and a four-year-old son. You never met them, because of your…accident. I'm looking forward to introducing you."

"I'm so excited," Izuku said, although he had no idea what to think about meeting himself as a toddler. Were they going to cause time paradoxes just by being in the same room? It was too late to worry about it now.

What had happened to the real First, now that Izuku had stolen his body? Hopefully he was still hanging around All Might with the other vestiges. Even so, Izuku felt guilty about his inadvertent theft.

There was no trace of One for All in his current body, which limited his options. He looked around the room.

Rather than a hospital, this place looked more like a mad scientist's laboratory. Countless tubes ran from his capsule to humming machines and a complex series of funnels and beakers. A giant microscope had a small metal hand attached to it. On the wall behind him, metal tubes and electric circuits spread out like an octopus' tentacles. A glowing ball hung overhead, crackling with energy.

Izuku shook an ice crystal off his white hair. Had this body been frozen? He only wore white hospital clothing. Goosebumps ran up his thin arms. He shivered.

Noticing, Hisashi took off his coat and put it around his shoulders. "I'll bring Dr. Garaki to take a look at you."

As he turned away, he didn't notice how Izuku's face clenched at the name.

Dr. Garaki was in this building. Izuku could kill the man and save the world. Save everyone he loved.

Except he probably only had one shot at this. If he failed, Hisashi would either toss him in a bank vault or eliminate him as an imposter. He had to be smart and wait for the right moment.

Yet as the doctor entered, Izuku shook from head to toe with rage and hatred.

"Here, let me check your vitals." Dr. Garaki held up what appeared to be a normal blood pressure cuff.

Izuku's teeth ground with the effort of not tearing the man's throat out.

"What's wrong?" Hisashi asked, frowning.

Izuku almost said nothing, but that might be more suspicious. "I don't know. I have this odd sensation I've seen this man before, but that can't be the case if I've been asleep so long. Does he look like someone else we know?" He didn't need to fake his shiver. "It's not a good memory. He was a bad man."

All for One blinked. "I'm not sure who you're talking about. It's been centur—" His face paled at his near slipup. "I mean, of course I know who you're talking about! That guy! He was absolutely awful, I agree. Uh…who was he again?"

Izuku took shameless advantage of his father's poor memory of the distant past. "I'm sorry, I don't remember anything. I just get such a bad feeling around that horrible puffy mustache and those beady eyes."

Looking offended, the doctor asked, "Am I taking his blood pressure or not?"

"I'll do it." Hisashi took the cuff. "You can leave."

Doctor Garaki stood up, muttering, "Worthless traitor."

Loudly, Izuku asked, "Did you just call me a traitor?"

Hisashi's lips peeled back into a snarl. "Get out. We'll discuss this later," he growled at the white-faced doctor.

Behind him, Izuku smiled widely. "That seems like a very strange insult. Traitor? What is this, a feudal monarchy?" He laughed.

"He's a very eccentric fellow," Hisashi said from between clenched teeth. "I'll have a word with him later."

Whimpering in terror, Dr. Garaki scampered out of the room. Any petty revenge Izuku could take on the mass-murderer gave him a warm, fuzzy feeling.

Izuku's fists finally relaxed after the door closed behind the doctor.

All for One had always claimed he'd had no part in what Dr. Garaki had done. Izuku actually believed it, because he didn't think the villain wanted to rule over a pile of ashes. In fact, he was fairly certain All for One had been the one to kill Dr. Garaki in the future. Far too late. However, since Hisashi lacked his future knowledge, he definitely wouldn't stand by and let Izuku murder such a useful minion right now.

Could Izuku expose Dr. Garaki's plans? What if he hadn't even started them at this point in time? His fingers twitched. If he could just get his hands around the man's throat, then he didn't care what happened to him afterward. His goals, in order of importance: stop Dr. Garaki from unleashing the end of the world. Protect the people he cared about. Stop All for One. His own survival came at the end of the list.

When his father spoke, it startled Izuku from his thoughts. Hisashi held up the blood pressure cuff. "By your standards, you're in pretty good health. In other words, you're an invalid by normal people standards." He smiled as if at an inside joke. "Let's get you some clothes. Then I'll find somewhere for you to sleep—" His phone rang.

Hisashi frowned. "Only emergency calls use that ringtone. I have to take this." A glint in his eyes promised murder if there wasn't a good reason for this interruption. He stood up and moved behind a tall metallic scanner, speaking in a low voice.

Then he screamed, "My son broke both his arms and right leg?"

This immediately grabbed Izuku's attention. He remembered no such incident from his own childhood. How could he have possibly changed the course of time already, when he'd yet to do anything except wake up? Broken limbs…that reminded him of the good old days with One for All. Surely it couldn't be. Why would his quirk have ended up inside his younger body when he hadn't?

Hisashi screamed even louder, "A punctured lung? Fractured skull? Internal hemorrhaging? Bring him here! Divert the ambulance! I don't trust some unknown idiot with a medical degree when my darling baby's life hangs in balance!"

When Hisashi emerged from behind the scanner, he looked like he'd aged years. "Yuuto, can you wait here? My son has injured himself as a result of manifesting his quirk."

"Of course. What was my nephew's name again? Izuku? Izuku's safety must come first." He forced his face into a fake look of concern. After everything he'd been through, Izuku could no longer place any value on his own life, but he did hope his younger self would survive for his poor mother's sake.

Not long after Hisashi left, a commotion of shouting people and the sound of gurney wheels echoed down the corridor. Izuku put his ear to the wall. It sounded like his younger self had been taken to the room next door. This must be the medical wing of the villainous fortress.

Izuku walked to the door. Sure enough, it was locked. His dear supervillain father might be trying his hardest to pretend everything was normal, but he hadn't gotten quite so careless.

With the equipment in the room, Izuku was sure he could break the lock easily. He hesitated. On the one hand, he might end up under tighter security if he pulled such a trick so early. On the other hand, preventing All for One from getting One for All was a top priority. He had to confirm if the quirk had ended up where he feared. Maybe he could slip over to the neighboring room, then get back before anyone noticed.

Izuku pushed open the door to the illicit hospital room. His four-year-old self was covered almost head to toe with bandages. His broken leg had been suspended from a sling. Both his broken arms crossed over his chest. The casts went all the way up to his shoulders. A bandage covered most of his green hair. He looked so pale that even Izuku felt sorry for himself.

One green eye cracked open. Then both of the child's eyes shot wide open and his casts rattled. Urgently, his younger voice called, "Izuku? It's Izuku in there, isn't it?"

Izuku recoiled. How could his childhood self possibly know that? No, it couldn't be him asking that question, could it? Then who had ended up in his body? He eyed the hospital patient with suspicion.

The child hissed in frustration. "It's me! Yuuto Shigaraki!"

Izuku gaped. "First?"

OMAKE TIME!

Omake: How All for One Survived Quirk Singularity

Hisashi: Ahhhhhhhhhhh! My quirks are going out of control! Quick, unload them all onto other people!

Moments later, All for One stands among a pile of corpses.

Hisashi: My beloved quirks, all gone! Clearly I'm the real victim here.

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Omake: Older Sibling Stress Levels Rising

Author: Yuuto, you've returned to life for less than an hour and already nearly died? Please pull yourself together. I have crack fic to write and I can't have you derailing this into a tragedy.

Hisashi: (Breaking through the fourth wall to interject himself.) Now you do see why I stuck him in a bank vault?

Author: Hmm…As an older sibling, of course I see your point…

Yuuto: Hey, what's that supposed to mean? You're acting as if I make a habit of near-death accidents.

Hisashi: YES YOU DO.

Author: Younger siblings, man. I get you.

Yuuto: As if Izuku isn't just as bad as me.

Hisashi: If you think that argument will make me less likely to vault you, you're very wrong.

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Omake: Custody Battle's Hisashi Continues to Poke His Head Into Other Fics

Custody Battle's Hisashi: This little brother has amnesia? How convenient. I'm still looking for some other universe's All for One to trade brothers with…

Author: The amnesia is fake and it's actually Izuku in there. Yuuto is in Izuku's body.

Custody Battle's Hisashi: Never mind. I'm not touching that situation with a ten foot pole.

Author's Note: Tunafishprincess posted a lovely prompt with both time-travel and body-swapping. How could I resist two of my favorite tropes? And then B_O_M_B suggested there be fake amnesia and mind games. It had me drooling. I promise there will be LOADS of three-way fake identity mind games. Thanks so much to both of you!

In this story, All for One took his younger brother's severely injured body after their fight and spent a century trying to heal it. He actually succeeded, and the only reason his brother never woke up was because his consciousness was floating around the Void. All for One would be severely pissed if he knew. On the upside, free body for Izuku!

Concerning why the First's name is Yuuto: this story is loosely connected to my stories Custody Battle and Karma Quirk, and uses the same characterization for the First One for All User. I'd already gotten attached to calling the First Yuuto before the canon name reveal, so I retconned an explanation: the First's birthname was Yuuto, but he changed it to Yoichi after becoming a hero in order take petty revenge on his older brother by calling himself "First Son." All for One would rather commit seppuku than call his little brother that, so he's going to keep using Yuuto for the rest of this story.

Bonus Omake: After Izuku Wakes Up and Fakes Amnesia

Hisashi: Let's go over the most important facts about you. To start with, your name is Yuuto.

Izuku: Uh-huh.

Hisashi: It definitely isn't Yoichi.

Izuku: That would be a rather strange name for a second son.

Hisashi: I'll kill every person in this room and then myself before I call you Yoichi. Because your name is Yuuto.

Izuku: We've established that, now can we move on?

Hisashi: You're not going to insist on being called Yoichi and refuse to answer to anything else?

Izuku: Of course not.

Hisashi: This amnesia may actually be genuine. Yes!