To understand things properly, we have to go back to years ago—back when Higashi Shuuichi had only just started working under Aizen. After Aizen effortlessly took control of Hueco Mundo, he quickly realized that the Menos-class Hollows were nothing more than paper tigers. They were nowhere near as powerful or terrifying as the Shinigami made them out to be.
Aizen, who had initially seen Hueco Mundo as an untapped goldmine, instantly lost interest.
So he turned his focus back to the Shinigami.
At that time, Aizen still firmly believed that only by delving deeper into the true potential of the Shinigami could one reach the unfathomable depths that would allow him to surpass Captain-Commander Yamamoto Genryūsai Shigekuni.
To that end, he chose one of Higashi Shuuichi's Shikai abilities—"Control the Soldier, Command the Man"—as a template to develop a custom-made technique for extracting reishi from Shinigami, rather than outright devouring them like Hollows did. It would serve his research far better.
But after only a few uses of this technique, Shuuichi quickly identified a massive flaw: unlike the nameless souls of Rukongai, every single Shinigami death would draw scrutiny from the Gotei 13, which would immediately increase security and patrols in response.
That made Aizen's method of gathering reishi from Shinigami painfully inefficient.
In an effort to prove his worth, Shuuichi personally proposed that Aizen modify the extraction technique so that it could be used without activating Shikai—making it less noticeable. Simultaneously, Shuuichi submitted a request to be transferred from the 10th Division to the 4th Division, arguing that the medical corps' constant contact with wounded Shinigami would give him the perfect cover.
To make the scheme work even under Captain Unohana's watchful eyes, Shuuichi had a further suggestion: weaken the amount of reishi extracted from each Shinigami. Just enough that they wouldn't notice or suffer impairment.
The trade-off was a smaller harvest per soul—but it came with near-total deniability. And given the sheer turnover of Shinigami in Seireitei, most would eventually pass through Shuuichi's hands at least once.
It was this caution that allowed Unohana to detect something off nearly ten years ago, yet never find the root cause. She simply couldn't pin it down.
That is, until two years ago—when she happened to see a seated officer from the 12th Division, Sarugaki Hiyori, flipping through old case records. A single file from decades ago triggered a hunch, and from there, Unohana began connecting the dots... and grew suspicious of Higashi Shuuichi.
Unfortunately, before she could act, a seemingly innocent promise made to Yamada Seinosuke alerted Shuuichi. The snake slithered away just in time.
To this day, Unohana Retsu has no solid proof. Only suspicions.
That's why Aizen said her current hesitation is, in a way, thanks to Shuuichi's early caution. If he had been even a little more reckless, she would've already made her move—maybe even two years ago.
Of course, Aizen never told Shuuichi this directly. These were conclusions Shuuichi reached himself after analyzing the data Aizen gave him.
After all, for someone like Aizen, digging into Unohana Retsu's past was child's play. Most of the young female Shinigami in the 4th Division couldn't resist the charm of that damned smile.
"But Aizen-sama," Shuuichi said as he closed the folder, concern evident in his voice, "even if everything you've said is true, Captain Unohana is still a threat. She may not have taken action yet, but her suspicions won't just vanish. If things go on like this, unless I stop working for you... something will eventually go wrong."
Honestly, Shuuichi wouldn't have minded if Aizen had simply chosen to eliminate Unohana altogether.
Once, maybe, he had felt something for the characters of the original timeline. But after living in the world of Bleach for over a century, that attachment had long since faded.
Now, his number one priority was survival. Everything else—loyalty, affection, sentiment—had to take a backseat unless they aligned with that goal.
And Unohana Retsu no longer fit the equation.
Unfortunately, Aizen wasn't eager to stir up another storm. He'd just orchestrated the deaths of two captains, enraging Central 46. With several others still chasing down Baraggan in Hueco Mundo, he didn't want to draw more attention.
"Then confront her," Aizen said simply.
To anyone else, those words might have sounded like calm advice. But to Shuuichi, they hit like a bomb.
"I don't understand, Aizen-sama. What do you mean?"
He was genuinely confused this time. What the hell was Aizen planning now?
"There's no way to make a move on Unohana in the short term," Aizen said. "So here's how you make the problem disappear: go find her, and tell her directly that you intend to fill one of the vacant captain positions—specifically the 10th Division.
"Depending on how she reacts, you'll know how far her suspicions go. If she insists on keeping you under watch—like Hirako Shinji does with me—then we'll adjust course.
"But if not? Then congratulations. You're qualified, both in strength and seniority, to become a captain."
Shuuichi stood in silence, his mind spinning.
With things said this clearly, it was hard not to think Aizen had been planning this from the start.
Had Aizen always intended for Shuuichi to take over a captain's seat?
It actually made perfect sense.
In the Gotei 13, captain's positions were strictly one-to-one: no vacancy, no promotion. Except for the 11th Division, but that post didn't suit Shuuichi's carefully cultivated persona—so Aizen would never put him there.
And Aizen himself had always been closely watched by Shinji Hirako. Even the slightest power spike might've prompted Hirako to act.
On top of that, captains rarely left Seireitei. Killing one inside the Soul Society was a whole different ballgame than doing it in Hueco Mundo or the World of the Living.
So now, Aizen was merely seizing an opportunity.
To Aizen, Unohana wasn't the real problem—she was only a threat to Shuuichi.
And this was the perfect chance to hit two birds with one stone: test Unohana, and possibly seat a new loyal captain.
It was clever.
But it left Shuuichi in a tight spot.
Aizen didn't know Unohana.
Shuuichi did.
She would never let him out of her sight.
Just like Hirako kept Aizen under surveillance, Unohana would keep him close—and call it "care."
Which meant: a one-sided war was coming.
And there would be no way to avoid it.
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