All for One would object if anyone claimed that he had an obsession with bank vaults. In fact, he considered it entirely logical to love vaults, those beautiful shining hermetically sealed metal containers impenetrable to force. As a child living on the streets, he'd longed for a safe place to sleep. Even a few hours of rest without other vagrants trying to steal his belongings or patrols of anti-metahuman groups trying to steal his life would have been a luxury. As an adult, striving to take control of an increasingly chaotic world, he'd craved the strength and certainty of steel, the cold uniform purity of it.

When All for One stole his very first bank vault, his brother had been pleased at their new place to sleep. (This was partly because All for One did not tell Yoichi that it had been stolen. He'd even scrubbed off the bloodstains first. By his early teenage years, he'd learned such tricks to handle intransigent can-throwing younger brothers.) Back then, Yoichi had been delighted for a place to sleep out of the rain and store his comic books. The two brothers had set about decorating their new home with Captain Hero drawings.

After a certain incident involving a dead Glowing Baby (more of a glowing teen at that point) Yoichi had tried to run away from home for the first time. This was clearly temporary insanity. Why would anyone with such a beautiful bank vault to live in ever want to leave? Yoichi would never survive on his own. Thus, All for One had used a quirk to repair a rusty unused lock, then sealed his brother inside the vault.

That had almost ended very badly because All for One had forgot about other people needing oxygen to breathe. In his defense, he'd stolen a quirk to bypass the biological need years ago. Also he'd rescued Yoichi before he had time to turn more than a little blue. Not that his dear little brother seemed to appreciate his speed, judging from the years of whining afterward.

Whether because of a very, very small mistake before the ventilator got put in, or because of the imprisonment, Yoichi stopped liking bank vaults after that.

All for One attempted to treat this obvious madness. His diagnosis: more bank vault time.

Yoichi reacted by going on a hunger strike. What illogic! First Yoichi complained about not getting necessities like oxygen, then he denied his own body food. This just went to prove that all younger siblings were completely irrational.

All for One tried many different tactics. He made Yoichi's favorite foods. He hired professional chefs to do a better job making Yoichi's favorite foods. In an attempt to invoke nostalgia, he stole some expired buns from the dumpster behind their childhood favorite convenience store, just like old times. He prepared a long speech about why Yoichi should eat, including a PowerPoint presentation. He'd even tried to hire a nutritionist for help but the man just kept whining about how he wanted his kidnapped family back. All for One had been certain Yoichi would break when his beloved comic books where taken away, yet still the fool held firm. Eventually he shoved food into his little brother's mouth screaming, "Eat it!"

At the end of his rope, All for One started considering the unthinkable—sharing power with his idiot brother. For All for One, giving up a quirk was the ultimate sacrifice. He felt certain Yoichi would be grateful for even a very weak one. But on the other hand, All for One liked being the stronger brother in every way. Also Yoichi was far too dim to use power effectively.

Fortunately, All for One never needed to resort to this dire tactic. Because before he found a weak stockpiling quirk, he found something even better.

A government assassin attacked All for One during one of his rare expeditions out alone. Once a week, he headed out to buy Demon King merchandise. He felt embarrassed to let his bodyguards see his hobby, even Machia. One of his employees had once hurt his feelings by referring to Captain Hero as a children's show and expressing amusement the boss could still be a fan at his age. Yes, All for One had brutally murdered that man, but his emotional scars lingered. To make matters even worse, the assassin's attack meant the government had uncovered his secret hobby. Now he had no choice except to conquer all of Japan in order to bury his embarrassment.

Of course the assassin was not the treasure. Her quirk was the prize. She had the ability to trap people's minds inside inanimate objects. She'd nearly managed to stick All for One in a Demon King figurine, which would have been cool, actually. However she'd needed to touch him to activate her ability, he'd been a tad faster, and now she was a smear on the pavement and he had a cool new power.

Only after All for One heard the sound of screaming from the pavement under the dead body did he realize that he'd accidentally stuck the assassin's soul in the road.

All for One ripped up a chunk of pavement and spent the next few hours experimenting. When the assassin was trapped in a rock, she could do nothing except curse at him. When in a plant, she could sway. When he stuck her in the Demon King figurine, she ran off the edge of the desk and broke the plastic arm. For that grave offense, he finally released the power and sent her back to her dead body (aka he murdered her.)

As All for One glued back on the arm, he felt indignant the government had tried to do such a horrible thing to him. Had they completely forgotten about human rights? About two seconds later, he started considering what would be fun to trap Yoichi inside.

A Demon King figurine? That would be hilarious, and Yoichi would hate it. But All for One didn't want his brother to be in a form that could move. He was too good at running away already. In a small body, he'd be even harder to find. Also, Yoichi could not be trusted to properly preserve a precious piece of Demon King merch. Why, the fool couldn't even keep his own body healthy.

What about a paperweight? All for One liked the idea of keeping his brother on his desk. The idiot would finally serve a purpose. Not a computer, Yoichi could get into far too much trouble as a computer. Perhaps a pen to sign his papers and force Yoichi to help with his evil empire despite all his stubborn defiance. Ah, but such tiny objects would be entirely too easy to lose. All for One preferred his dear little brother safely inside his beloved vault.

Just like that, inspiration struck. All for One could combine the two things he loved the most in the world by trapping Yoichi's soul inside a bank vault!

This new idea was absolutely perfect. It would keep Yoichi in the vault forever. How could he escape the vault if he was the vault? He would be unable to run away, try to sabotage All for One's business, or offer any meaningful resistance. It would ensure Yoichi's survival by giving him a tough steel body. He would no longer need food. No one would be able to harm him, nor would he be able to self-harm. Best of all, Yoichi would be completely unable to run away or put his hands over his ears as All for One recited his 500,000-word Demon King wins fanfiction. (No one had ever reached the end of the fanfic before, even his most loyal readers dropping off because of the long monologues and excessively gruesome torture.)

On that great thought, All for One ran downstairs to the vault to carry out his plan at once.

Yoichi crouched in the corner of the vault and glared up from under his hair. Such an ungrateful stare, after how All for One had shared his favorite possession with his little brother. No one else got allowed into the vault, not even his trusty Machia.

"Are you here to force a quirk on me?" Yoichi snarled. "I knew you'd try to use that same tactic to control me, just like how you control all your minions. But I'll never give in—"

All for One laughed loudly over his little brother's speech. "Nope, I have no intention of sharing my power with you. You'd probably find a way to disintegrate yourself with it. Instead, I have an even more generous offer. I'm going to share my most treasured possession with you."

Yoichi blinked up at him. "I'm already in the bank vault."

"Not as much as you're going to be!" All for One grabbed his brother's forehead. "In this new world, fantasy has become reality. And I've found a way to fulfil a particularly weird fantasy."

Almost immediately, Yoichi's body went limp. The walls of the vault shuddered. Then Yoichi's voice came from them: "What have you done to me, brother? No. NOOOOOOOOOOOOO!"

"Well, that's gratitude for you," All for One said irritably. "I turn you from a weak and pathetic fool to the most magnificent object in existence, and you're still not happy." The screaming was getting on his nerves, and Yoichi was clearly in no state to listen to reason, so he left.

When All for One next returned, he installed his brother's body in a carefully prepared glass capsule designed to keep it in stasis. He'd learned from his experiment with the assassin—he must keep the body in good shape, just in case he ever needed to release the quirk or (heaven forbid) something damaged his vault.

Stepping backward, All for One admired his work. He had his brother's body, his brother's soul, and his entire collection of Demon King merchandise lining the walls of the vault. All of his most beloved possessions were together. Truly this was his greatest accomplishment, besides maintaining a healthy work-life balance while also spending time on his hobbies.

All for One settled into a comfortable arm chair and pulled up his fanfiction on his tablet. "How are you settling in, Yoichi?"

The walls remained quiet. Perhaps Yoichi had resorted to the silent treatment again. It never lasted—All for One knew exactly how to push his little brother's buttons.

Smirking, All for One said, "I thought you might be bored, so I brought you some reading material." He would swear the air got slightly colder.

The tablet made a fizzing sound, then the screen went black. All for One shook it. "Hey! Yoichi, did you do that somehow?"

He'd been mostly joking. But then the door slammed shut.

All for One leapt to his feet. The lock had been sealed. He tried several quirks, but nothing could break through. He'd designed this particular vault to be completely impenetrable. He had to stop for fear of damaging his beloved vault.

Leaning against the wall, All for One panted. "Very funny. For your information, I have backup copies of all my fanfics."

Yoichi's voice echoed from the metal. "How do you like being locked inside your own vault?"

"I happen to love bank vaults." All for One scowled. He'd been sincere, but also bluffing. It would be very embarrassing if his subordinates found him locked in here. "How did you do this? When I experimented with the quirk, people trapped inside inanimate objects couldn't move."

"I couldn't move either, at first. I played around with the power."

All for One sighed. "This is why I'm glad I didn't give you a quirk. You probably would have turned it into an entire legacy of heroes dedicated to destroying me."

"You mean forced a quirk on me. It's not a gift if I don't accept it."

"Agree to disagree."

Yoichi's tone turned malicious. "Then I'm 're-gifting' your vault to you. Don't you know it's rude to refuse gifts, big brother?"

"You're bluffing. I know you don't actually want me around forever."

"If I have to remain trapped in here forever, then so do you. Or you could give me back my body, then I won't be able to seal the door shut." Yoichi's tone was a bit too casual. Clearly this had been his aim all along.

"It wouldn't do me any good. I carefully designed the security system not to open from the inside." And of course Yoichi wouldn't open the door before getting his body back because he knew he couldn't trust his brother to keep the deal. There was no point in even offering. All for One sat back down. "We're both stuck here until someone opens the door from the outside." He did not feel too worried. Machia would come looking for him within a few hours. His bodyguard kept a close eye on his schedule.

Yoichi groaned. "And to think you call me a fool."

"I'm perfectly fine being inside a lovely vault." All for One crossed his arms.

"We'll see how long that lasts. I'm going to make your life a living hell until you give my body back." Yoichi raised his voice. "The Demon King is a flat and one-dimensional character. The author made him stupidly OP but he's not very bright. He'd have lost in the first volume if not for plot convenience."

This was a familiar speech, yet it never failed to provoke. Face reddening, All for One shouted back, "Haven't you swapped the Demon King with your meathead of a hero?"

Yoichi's voice filled with the depths of metal, becoming unnaturally loud. "You only like his dress style, you'd hate the Demon King if you ever met him! Two people with such giant egos couldn't fit into one room."

For the next three hours, the brothers tried to out-shout each other. All for One had a piercing headache, though he would never admit defeat. He missed the sound of the door opening.

Until Machia said, "Lord, I apologize for disturbing you, but you have an important meeting with the local yazuka boss in ten minutes."

All for One whirled around. "Machia, fetch my fanfiction so I can teach my foolish little brother—"

He'd spoken too late. Machia stepped into the vault, and the door slammed shut behind him.

"That was the sound of the automatic lock clicking shut," All for One growled. "Great job, Machia."

Unfortunately, Machia was completely immune to sarcasm. The bodyguard beamed. "I will stay here as long as you desire, Lord." His gaze became dreamy. "Just the two of us, locked in a tightly enclosed space. I've dreamt of this scenario many times…"

Loudy, Yoichi said, "I'm here too. Watching everything you do. Go on."

Machia paled. "Is that the idiot brother?"

"Yup, Yoichi turned into a bank vault," All for One said, conveniently leaving out his own culpability. "What a fool, am I right?"

"The real fools are the people trapped in here while I completely control the environment," Yoichi said. The air grew hotter as if reflecting his fury.

Machia turned even paler. "We've got to get out of here."

"I welcome your suggestions." All for One sighed, depressed he'd come to the point of saying that even sarcastically. "Don't you dare damage my vault, though."

For the next couple hours, Machia tried lightly patting the walls and picking the lock. Not that Machia had any ability to pick locks. Also, the lock was on the wrong side of the door.

Yoichi at least dropped the subject of Captain Hero now he had an audience. Instead, Yoichi kept making jokes about rom com scenarios and someone's secret crush that he might reveal. These words left Machia flustered and more and more desperate to escape. Finally, Machia punched a wall.

"Hey! You might dent my beloved walls," All for One cried. He suspected his brother was targeting Machia as the easier to provoke one, and it seemed to be working. Poor Machia was an only child. He had no immunity to the incredible annoyance power of younger siblings.

Machia wrung his hands. "Lord, how else can we escape this hell? Please share your wisdom."

In a sing-song voice, Yoichi said, "Wisdom? What wisdom? My brother is completely oblivious to everyone around him…especially their feelings…"

Machia raised his fist.

"I approve of hitting my brother, but not my vault," All for One snapped.

Yoichi giggled. "Machia, we might not always get along, but at least you're better than the creepy doctor who also likes my—"

"Not one more word!" Machia bellowed.

All for One put his hands over his ears. "Do you two never shut up?" At least this teasing was slightly better than when Yoichi had decided to sing the Captain Hero theme song fifty times in a row.

When the door opened again, All for One whirled around, about to promise any favor to the person who had freed him from this nonsense.

Garaki stood in the doorway. "There you are, master. You were supposed to visit my lab to see my latest creation."

All for One changed his mind because he instinctively feared what favor the doctor might ask. "Stay where you are! Don't take one step forward."

Garaki froze, but it didn't save him. The door slammed shut, hitting him on the bottom and knocking him into the vault. Only one sliver of light remained, the width of a spider's thread dangling into hell. And it was vanishing fast.

All for One wailed, "Yoichi, stop! I'll give your body back! Just don't you dare leave me trapped with him!"

The good news was that All for One had slammed Yoichi's soul back into his body before the door completely closed. The bad news was that his plan to perfectly contain his brother had been an embarrassing mistake, his subordinates knew he'd been locked in his own vault, and he'd failed to obtain a valuable alliance with the yakuza.

At least All for One had made it out the door while Yoichi had still been dazed inside his glass capsule. Yoichi remained in the vault, where he belonged. And All for One would have time to figure out a better place to stick his brother's soul. He'd never met a mistake that he didn't believe could be turned into a success by trying the same thing again.

Whistling, All for One climbed down the stairs to his vault. "Little brother, how would you like to be a Demon King poster? Paper would be less mobile than a figurine. You'd be so much more handsome that way."

A horrific sight greeted All for One: a dented vault door, fallen off its hinges and stained with soot.

"NOOOOOOOOOOOOOOOOOOOOO!" All for One dropped to his knees and shook his fists at the ceiling. "My vault! My precious vault!" He gathered the door into his arms. "Surely this damage can be repaired." His fingers traced each unforgiveable dent and scratch. "My beloved will be avenged." Someone had done this to his treasure. Someone he would hunt down and slaughter. No expense would be spared in his revenge. This meant war!

Oh, yeah, his little brother was missing too.

OMAKE TIME!

All for One: My bank vault is my favorite possession in the world.

Yoichi: I'm relieved to learn that I don't count as a possession.

All for One: What are you talking about? You're a very close second.

#

All for One: I'm shocked, utterly shocked, that the government would try to trap my soul in an object. They didn't even give me a fair trial. This is cruel and unusual punishment.

Yoichi: You did the exact same thing to me.

All for One: Yes, but I'm a villain, it's expected when I do it.

Yoichi: Your argument is bullshit. Plenty of people expect the government to be evil and our current regime has a particularly low approval rating, so they could use the same reasoning as you. Not that I want to be in the position of defending our current military dictatorship. By their standards, they were being lenient in leaving you sort of alive.

All for One: They probably wanted to threaten me into using my ability for them.

Yoichi: Whoa, they suck even worse than you.

All for One: Take that back! I'm the most evil!

#

All for One: The only downside to trapping my brother in a vault is that I can't hug him now.

Yoichi: I'll never have a love life in this state!

All for One: Just like that, I have made my peace with the tradeoff.

#

Yoichi: Let me out of this glass coffin! You're probably not taking care of my hair properly.

All for One: I'll hose you off every couple weeks.

Yoichi: HOW DARE YOU? IT'S ON NOW!

#

All for One: Trapping my brother in a vault is old news, turning him into a vault is the new thing.

Yoichi: Fool! You haven't trapped me, I've trapped you!

All for One: Aww, you vaulted me! You really do love me.

Yoichi: You're trapped away from the Demon King merchandise you left in your office and bedroom. I bet Garaki will play with your figurines while you're gone.

All for One: LET ME OUT OF HERE!

#

All for One: Nothing could persuade me to release my brother from the vault.

Garaki: All for One, I'm here to save you! And I guess save your stupid bodyguard too. Then you'll owe me a favor.

All for One: One thing would persuade me to release my brother from the vault.

#

Yoichi: It's great to be back in my own body. Yes, I'm still imprisoned by my demented older brother, but I have to take my small victories where I can find them.

All for One: I could move your soul to a healthier body. Why didn't I think of that sooner? I guess because I was too busy literally vaulting you.

Yoichi: Don't you dare take away my perfect hair.

All for One: I thought you'd object to stealing someone else's body.

Yoichi: That, too. But I need my beautiful hair in order to seduce a hero into rescuing me.

#

All for One: I've got the perfect idea! I should have trapped Yoichi inside my own body instead. Then it would have been just like I'd absorbed him in the womb. Also, I consider my hair to be even better than my brother's so he will trade up. I'll correct my mistake right now. Hey! Why is my vault empty?

Yoichi: Phew, my hero got me out of there just in time.

Kudou: Yeah, no matter how much I adore you, I couldn't have taken you with me if you came with All for One attached. His hair is too ugly.