A oneshot
I don't own Bleach. The author has it well in hand anyway, so I wouldn't change anything even if I did own it.
And this is not a slash pairing.
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Aizen Sousuke had wanted only two things since he was a child: To be greater than any who had come before him, and in turn be acknowledged by the King of Soul Society himself. As he worked he way up through the ranks of the shinigami, however, he realized something. The shinigami's powers, by definition, were limited. It was true, one could become immensely powerful through use of Bankai, but that was it. After Bankai, what was there? And so, Aizen's research into something stronger than Bankai began.
Slowly but surely over the following years, Aizen became frustrated by the limitations of shinigami powers. He had worked and worked, but was unable to even find another barrier to break beyond Bankai. He had become more powerful than any person before him, and yet he was still limited. For one of Aizen's mindset and genius, this was an insult to everything he stood for. It could not be possible that he could stop growing. As the shinigami were simply spirits, their mind should be their limiter, not their body; and yet, this seemed not to be the case. However, after encountering a primitive Arrancar during an expedition to Hueco Mundo, Aizen's inner scientist was intrigued. Here was a creature, while rather pitiful compared to his own power, whose combined shinigami and hollow powers were greater than those individual powers might otherwise be. Perhaps this was the answer he had been seeking?
Delving further into the mysteries of the Arrancar and the so-called Vizard, Aizen discovered that these hybrids, these fusions, after their ascension, had become far, far more powerful than their original forms.
In the course of his research, Aizen met one whom he thought shared his goals; a young shinigami captain, close to his own age, by the name of Urahara Kisuke. Both men shared the same lust for knowledge, but for different reasons. Urahara simply wanted knowledge for knowledge's sake, while Aizen wanted it for more power.
This was another trait the two of them shared; both liked holding power over others. Urahara liked it because it was fun to play jokes on people; he had always thought Aizen needed to loosen up, though in later conversations he would admit using his newfound knowledge of the Captain's birthday to hire him an entire harem's worth of prostitutes was a Bad Idea. It got even worse when one of them turned out to actually be Kurotsuchi Mayuri's 'daughter' Nemu, who had been attempting to learn more of social activities, and had wandered into exactly the wrong bar at exactly the wrong time. And it passed 'Bad' and went straight into 'Disastrous' when most of the women later turned out to be members of the Aizen-taichou fanclub, a group Aizen had successfully avoided any contact with for centuries.
Those of Soul Society who were permitted to recall that Event by Aizen still remember that day as "The Dawn of Aizen's Wrath". Urahara remembers it as "the day the bastard finally got some. Well, probably. Maybe. You know, I wish he had been more coherent while trying to kill me. I could have learned so much more if that was the case."
Aizen chose to suppress the details of most of his memories of that day using his zanpakuto, as the main layer of the elaborate prank had involved a teleportation device targeted at him, as well as a time bomb with a note attached, saying that one of the women knew the deactivation code, but had been ordered not to tell unless certain conditions were met; suffice to say he did not arrive or exit the room at his destination fully clothed.
Ichimaru Gin still laughs at the picture Urahara had sent him; a priceless image of a stunned, blushing, very embarrassed, and out of his depth Sousuke Aizen, clad in only his underclothing, as well as a bit of something on the edge of the picture that looks suspiciously like a large group of female hands, lunging for their prey. He did, however, keep it a secret from Aizen that he knows all the details of the Event.
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It had always been like this for the two of them, Aizen calm and collected on the outside, Urahara never missing a laugh to be had, or a joke to be played. But now, as Aizen stood before Heaven's Gates, Urahara stood in his path.
"So...it has come to this, Urahara-san."
For once in his life, Urahara Kisuke had a grim expression on his shadowed face, his trademark hat shading his eyes.
"So it has, Sousuke-kun. I suppose you're going to try and get past me, then?"
"Try? Why would I need to try? I have achieved near-ultimate power...all that remains is to claim my rightful place. And no one, not even you shall stop me."
"Really? Well now, that is interesting. I wonder why I'm standing here then?" Urahara's expression lightened suddenly, and he grinned cheekily at Aizen.
"Move from my path, or perish. Either way, I will finally be rid of your inanity."
"Before we begin, Sousuke-kun, I'd like to ask you something."
"Make it quick." said Aizen irritably. He had not made it this far to be stopped by this...clown.
"Did you take into account the fact that your zanpakuto might not be the only one with hypnotic powers?" Urahara began to laugh.
However, even as Aizen started in surprise and dashed forward, the world began to dissolve around him.
"Shakou Seishin, Benihime!"
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This idea just came to me in my insomnia. I couldn't sleep, so I wrote this instead. As such, it may be rather disjointed. I apologize for this.
Also, Shakou Seishin, if I did it correctly, should translate to 'Darken the Mind.' However, given my utter lack of any practical knowledge of the Japanese language, this may be incorrect.
Anyway, comments and criticisms are all welcome; this will most likely not be continued or expanded, it was just a plot bunny that demanded to be written.