The Mk ∞.

Muken ... a voided space completely sealed off from the outside world, aside from the main tower that serves as the entrance and exit. The vast darkness gives the illusion that it stretches on infinitely. 

Under normal circumstances, non-criminals are not permitted entrance, but Retsu Unohana managed to gain permission from Captain-Commander Shunsui Kyōraku to use the location as a battlefield to train Kenpachi Zaraki in the future. 

The Muken is reserved for criminals whose hearts cannot be stopped by any means by executioners. It is impossible and illegal to enter the Muken without permission of the Head Captain of the 13 Court Guard Squads. And yet in the darkness of the Muken, two figures stood opposite to each other. 

Yachiru Unohana, one of the most dangerous and notorious criminals of Soul Society stood opposite her disciple and Lieutenant, Toji Fushiguro. Or rather ... Gremmy. Quite a few years have already passed since Toji has become the Lieutenant of the 11th Division to become Unohana's disciple.

A lot has happened over the roughly 100 years and Toji has been enjoying himself. As a Lieutenant of the 11th Division, he didn't have that much to do, surprisingly. He selected a competent 4th Seat and a very strong 3rd Seat. Distribution of work was important and it allowed Toji to pretty much do whatever he wished. 

He had been learning Zanjutsu from Unohana since the beginning of his time as her Lieutenant and his progress was ... monstrous to say the least. Toji has surpassed her, while only showing great progress to her. He enjoyed their fights and didn't want her ... obsession ... to increase. 

He had noticed that Unohana was not entirely sane. And it seemed that she had developed some form of unhealthy obsession with all things that are related to Toji. He wondered if this was what a Yandere was like. If so ... then he would have to prepare his full power of imagination to get away...

It had worked for now. He usually found a way to minimize the time he spent with her by 'doing his duties'. But it didn't work out as well as he hoped. She usually forced him to spend time with her ... and that was mostly spent fighting. 

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Over the years some Captains have died already. It was inevitable as none of them survived till the Canon events, apart from Unohana and Yamamoto. But the way they died was not always as he imagined.

There were a few executions due to the dangers they posed or crimes they committed as well as death due to an experiment that backfired and some reckless fighting against ... oh I don't know ... like 5 Vasto Lorde at once. They were seriously lunatics. But he enjoyed his time here and would actually call quite a few Captains his friends. 

Toji was also not entirely innocent to the Captains dying. But we shall not talk about that for now.

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Unohana, known for her battle mania and queenly expression, regarded her opponent with an almost serene intensity. Her love for crossing blades was an intoxicating passion she wore like a badge. That is something she would hide in the future, but for now, she looked ever the dangerous Kenpachi that she was. 

With her Zanpakuto in hand, she was a sight to behold, a warrior poised and ready for battle. A blade ready to cut the enemy mercilessly to pieces. 

Toji, on the other hand, possessed a powerful physique that embodied raw strength. He was the embodiment of carefreeness. His grin was a testament to his sheer enthusiasm for combat. While not as much of a battle maniac as Unohana, he revelled in the thrill of a good fight. 

His eyes twinkled with the excitement of facing a formidable adversary. Even if the intensity of Unohana's interest in him ... scared him ... he enjoyed their fights to the fullest. It seemed Kenpachi Zaraki was right, the strongest will always want to fight the other strong. And Toji was no exception. But he knew that he was truly powerful and wasn't as dependent on fighting as others.

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The duel began with a graceful display of deadly precision from Unohana. Her movements were a combination of elegance and murderous intent, showcasing her mastery of many techniques. Each of her strikes was executed with exquisite precision, leaving behind a trail of shimmering afterimages as her Zanpakuto sliced through the air like a phantom and clashed with Toji's.

Toji met Unohana's assault with a display of raw power and blinding speed. With every clash of their Zanpakuto, sparks ignited in the dark Muken. 

They weren't even allowed to be there. Toji had figured out a way to change the matter and open a Garganta with it. He used all his free time to train his imagination and multitask as well as battle with creatures or characters that he created. 

Toji defended against her onslaught with an almost casual air, his grin widening with each successful block and parry. He enjoyed himself and couldn't help but smile. It was something that came automatically whenever he fought Unohana. It seemed like she had ruined him ... poor Toji. 

Unohana's calm expression wavered slightly as she realized that Toji's incredible strength easily matched her finesse. It was a fact that gnawed at her competitive spirit, but she remained composed. She knew that Toji was not giving it his all. And that angered her but said anger didn't show on her face. 

With a graceful step backwards, Unohana created a brief separation, allowing herself to recalibrate. Her eyes never left Toji as she weighed her options. She had a deep admiration for her opponent's skill, a rare quality that intrigued her. She herself didn't understand her 'interest' in Toji, but she knew that he got more and more interesting the longer she knew him.

Unohana was not one to back down from a challenge. With increased determination, she launched herself forward once more, her Zanpakuto cutting through the air with deadly precision. Her aura radiated intensity and purpose as she confronted Toji in another round of combat. Her bloodlust was shooting through the roof and her excitement was almost visible.

Their blades collided in a mesmerizing dance, the clashing of steel echoing through the Muken. Unohana's technique was a breathtaking display of beauty and deadly martial prowess, while Toji's every strike was powered by raw, unyielding force. That didn't mean he was less skilled than her, on the contrary. He was just as skilled with the blade as her.

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Unohana's expression, now marked with a bloodthirsty smile, stood in stark contrast to Toji's seemingly arrogant grin. Unohana's expression amused him, but he didn't want her to think that he disrespected her. 

The spectacle was a testament to the profound love they both held for the art of ... sword fighting. Although they both just liked to fight. Unohana had also been teaching Toji Kaido, the healing Kido that she had been taught by Tenjirō Kirinji. 

It was a fast and unpredictable exchange of blows and parries, a mesmerizing dance of death, with the Muken as their silent audience.

The clash of their swords resounded through the darkness that was the prison Muken. The duel continued, a ruthless pursuit of excellence in swordplay, as Unohana pushed her limits and Toji matched her blow for blow.

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"So are you going on another ... gang extermination trip?", Toji asked Unohana as they were enjoying some tea together. 

"Hmm ... you paused there. Why?"

"You know why."

"I do not.", Unohana said.

"Haa, you are obviously not doing it to do your duty. You could let someone else handle it. We have been doing this for so long already, why are you still pretending?"

"It amuses me to see your annoyed face.", Unohana said with a small smile.

A tick mark appeared on Tojis head. This woman would be the death of him ... at least mentally. He had to take another time off from her. She was starting to show the strange behaviour again.

"I don't like that look. You're not thinking of running away again ... are you ... To-ji?", Unohana said with killing intent.

"What? I never do something like that! The Squad just sometimes needs my expert handling, is all...", Toji smiled a very strained smile.

'How in the world did she figure that out? This is far too scary, should I transfer to another Division...'

Toji thought in his head.

A hand suddenly touched his shoulder, pulling him out of his thoughts. He looked to see a smiling Unohana looking at him with closed eyes. 

"Toji why do I feel like you thought something disobedient just now?", Unohana said and opened her eyes slightly at the end.

A shiver ran down his back when he saw her. He was by no means a beta male, but he came from the streets and he never had to deal with something of Unohana's calibre. Any woman actually. He had no experience. 

"You will accompany me today.", Unohana said with finality. 

"Haa, alright."

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Unohana and Toji walked through the Rukongai. They were dealing with gangs. Or Unohana was. Toji was doing something else. He had a very peculiar device in his hands. It was a small, bluish-purple orb with a strange substance inside that looked like it had falling stars inside. 

The orb itself was also special. It looked to be silver in colour and had an almost dreamy shine to it. 

This was the Hogyoku. Or as Toji liked to call it: The Hogyoku Mk. ∞. It was going to be the ultimate Hogyoku and Toji added some very special things to it. 

Since coming under Unohana in the 11th Division and being her Lieutenant, he has gone on a lot of such 'removals' of gangs in the Rukongai. And Toji thought about one of his weaknesses. He was still only imagining his body.

There was also the fact that whatever he imagined would disappear once he took his mind off it. That was a weakness that would go away the more he trained as he got more powerful. But why train when you can just imagine being more powerful?

So what did he do? He took advantage of the 'murderous' times that the Soul Society was still in and created a Hogyoku for himself.

But not just a normal one. No. He added something special to the mix. He thought about how to make the Hogyoku more powerful and he found his answer in the comics he used to read.

There were many powerful metals and materials and he wanted to use some of them to create the Hogyoku. And that is what he did. He created the 'container' that was the Hogyoku out of three powerful metals. 

Element X, Pure Adamantium and Volatile Prometheum. Element X and Prometheum were from the DC universe and Pure Adamantium was from the Marvel universe.

Why did he choose these three? Simple.

Element X was a very special material, with which Toji felt a close connection. The Element X is a metal of pure imagination personified, having the ability to shape and materialize anything the user can think of and make it into reality. Now imagine that. A metal that was the same as he was. 

He could feel the connection the moment he imagined it into existence. And because he wanted it to not disappear when he lost concentration, as unlikely as that sounded nowadays, the metal would never disappear.

Seeing his success, Toji continued. Fueled by the desire to do the impossible, he then imagined volatile Prometheum.

Volatile Prometheum is a special metal that is capable of channelling, amplifying and perpetuating near-limitless amounts of energy. 

As such it was used as a power source for many gadgets or to create the most destructive arms imaginable, in the DC comics. 

However, this "volatile promethium" is a dangerous mutagen that can be used to mutate living beings or trigger their metagene. At least that was usually the case. Toji imagined it to just ... not do that and it worked.

The last metal was Pure Adamantium from Marvel Comics. While Toji chose Element X because of the close connection it had with him and the power of imagining things into reality, Volatile Prometheum for the near limitless energy reserves it provided, he chose Pure Adamantium because of its durability.

It is the absolutely most indestructible item in all of existence, in Marvel. Even if it has been broken five times, those are not things we want to think about right now.

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So Toji took all of these three metals and then imagined them to fuse together and create a completely new and improved metal that was never seen before. This process took A LOT out of him and he had to take a long nap after completing the process. 

When he woke up, he held an empty 'Hogyoku' in his hands that was ready to be filled with whatever he was willing to provide.