Rewind a bit.
Inside the 5th Squad barracks, at the dojo.
A youth wearing plain glasses and with slightly wavy brown hair was hunched over his desk. Unlike the usual paperwork, the documents he was currently handling included research records from his previous experiments.
Due to the recent Zanpakutō rebellion, the Captain of the 5th Squad, Hirako Shinji, had been caught off guard and thoroughly humiliated by a certain someone.
Though luck had played a significant factor, it was an undeniable fact that he had been beaten into critical condition.
Furthermore, his Zanpakutō had been shattered outright, requiring a tremendous amount of energy and training to restore it.
As a result, since regaining consciousness, Hirako Shinji had been residing in the 4th Squad's Comprehensive Relief Station.
With no one left to monitor him, Aizen Sōsuke naturally relaxed his guard. He took advantage of his free time to dive back into the research projects that had been piling up.
Aside from the crucial study on the spiritual boundary between Soul Reapers and Hollows, there were still many unresolved puzzles.
For instance, the energy of Hell, the secrets of Enrakyōten...
And Naraku Sora's perfect Hollowification.
Aizen quickly jotted down a few data points, organizing the potentially useful information into sections before calculating the correlations between them.
A long string of complex characters flowed smoothly from his brush.
Compared to the monotonous daily chores of a Lieutenant, Aizen much preferred this feeling of exploring the unknown.
He had originally expected it to take a long time to reach this stage.
However, since forming a collaborative alliance with a certain someone, his research progress had advanced at a breakneck pace.
Materials that would have previously required immense time and effort to track down were now often secured in a single outing.
Captain-level Soul Reapers, Arrancars who had broken their spiritual boundaries, Gillian-class Hollows on the verge of evolving into Adjuchas, and even a Zanpakutō capable of copying the powers of others...
Speaking of which, Naraku Sora had mentioned that once the heat died down, he would borrow Kuchiki Kōga's Muramasa for a while.
Aizen was extremely interested in an existence that could materialize the spirits of other Zanpakutō and even turn them against their masters.
If he weren't worried about exposing his identity, he might have even wanted to see what the materialized form of Kyōka Suigetsu would look like.
He had heard that some biological-type Zanpakutō could be modified; he wondered if a materialized spirit would meet the criteria for such a thing.
'Then again, with the techniques that fellow taught me, the value of Kyōka Suigetsu seems to have decreased quite a bit.'
Aizen thought this over while rapidly calculating values in his mind.
'Yes, there shouldn't be anything missing.'
Just as he was about to finalize the results, the scratching sound of his brush came to a sudden halt.
The smile on Aizen's face froze as he abruptly looked out the window.
A massive, volcanic eruption of spiritual pressure had suddenly burst forth within the Seireitei. It felt as if the sky itself were collapsing, the Reiatsu rolling outward in all directions with a suffocating weight.
Initially, Aizen didn't pay it much mind.
Even if an intruder like a Ryoka or a Menos Grande had broken into the Seireitei, other Captains would handle it.
At the very least, Head Captain Yamamoto was still there.
There was no need for him to worry.
But the moment that Reiatsu swept past him, he caught a very specific scent.
One he was all too familiar with.
Naraku Sora!
'How could that brat's signature be mixed in with this level of spiritual pressure?'
'Could this be a mess he caused?'
Aizen narrowed his eyes and released his sensory Reiatsu.
Since no one in the barracks could currently detect his true power, he could act with relative impunity.
After confirming the situation several times...
Aizen opened his eyes, a flicker of hesitation crossing his face.
Though he didn't know who the owner of that strange Reiatsu was, the blatant violence and malice in it suggested the situation on the ground was far worse than he had estimated.
A spark of white lightning flickered from his palm, instantly incinerating the data he had spent so long calculating.
A moment later, a Kidō shroud covered his body. With a blur of motion, Aizen vanished from the office.
Naraku Sora stared in shock at the creature before him.
To be accurate, it could no longer be called a person.
Tsunayashiro Taketori's severed head had been covered in black sludge and clumsily placed back onto the stump of his neck.
Looking at the scene, Sora felt a bit numb.
'Look, if you put it on straight, I could handle it. Even if it was a little crooked, I could accept that.'
'But how the hell do you end up with the top of your head plugged into your windpipe?!'
Though the process was a disaster, the result was effective.
Taketori opened his eyes. The multiple pupils within them carried an immense pressure; even a casual glance was enough to create an illusion of a heart attack.
The darkness was boiling.
The pitch-black shadows rippled, and to the sound of countless bones grinding against each other, eye after eye slowly blinked open.
The massive Reiatsu began to condense.
It switched from its original full-power mode to a concentrated, energy-saving mode.
This was a fundamental mutation—moving from an unrestrained cloak of power to a focused strike against a single target, shifting toward an even deeper domain.
It was like a transformation of a giant of light.
Accompanied by a frantic writhing and turbulent Reiatsu, the creature began to squeeze every ounce of infinite power from its body. A brand-new heart began to beat.
A pair of sharp, bull-like horns sprouted from the black muck. Shadows extended and wove themselves together, clinging to the mutated body to form a massive, centaur-like beast.
Twelve arms burst from its back, surrounding a bizarre bone mask that had emerged on its chest like stars around a moon.
Then, the arms reached up and placed the mask onto the upside-down head.
The monstrous entity stood upright and lowered its head. The dual pupils atop the bull head scanned the area before locking onto Naraku Sora.
A torrent of pitch-black Reiatsu rose from its frame.
A silent shriek erupted from the center of Ugendo.
Driven by instinct, Sora raised his right hand and released Bakudō #39, Enkōsen.
The silent shockwave materialized into a physical force. Everywhere it passed, everything was torn apart by its unreasonable, violent power. When it slammed into the oval shield, the barrier let out a sharp screech.
In the distance, Ukitake Jūshirō held his blade with one hand, absorbing the impact of the sound waves. Behind him lay the unconscious Kotsubaki Sentarō.
The aftershocks of such high-intensity combat were proving too much for a Soul Reaper who wasn't even a Lieutenant.
"Sora, don't hesitate! Run!"
"These are Soul King fragments that Taketori gathered in secret. They've gone completely berserk under some unknown power!"
"And its Reiatsu is locked onto you alone!"
Ukitake coughed up a large amount of blood but forced himself to finish his warning in one breath.
He was terrified that his junior disciple would charge in blindly again.
He knew that the power of the Soul King was on a completely different level compared to Gosuke or the previous Taketori.
Sora took a deep breath, his expression turning solemn.
It was roughly as he had suspected. This scene was indeed similar to a certain memory.
It was like when Yhwach absorbed the Soul King's body and the excess power spilled into the Soul Society, instantly turning into a flood of endless monsters that tore at the Soul Reapers in the ruins.
'How was that solved back then?'
There was no time to think. The bull head lowered, and its two eyes—containing four pupils—locked onto Sora simultaneously.
The moment their eyes met, a bizarre ripple spread.
It felt as if an invisible blade had been thrust into his soul. A sharp, intense pain exploded instantly.
It felt as if someone was stirring his brain with a knife.
"Cough—"
Sora hunched over, vomiting a pool of dark red blood.
By the time he managed to recover, a massive shadow had already enveloped him.
Eleven arms were raised. The remaining one picked up the Zanpakutō Taketori had dropped, and a torrential barrage of attacks poured down.
In an instant, Sora was submerged.
The suppression he had achieved earlier through raw power was now being returned to him without reservation.
Reiatsu surged like a tide. The dormant shadows became active again, condensing on the creature's arms to strike with unerring accuracy.
Sora was sent flying, crashing through the squad buildings and kicking up clouds of dust.
Two of the creature's arms mimicked the pose of drawing a bow. A massive amount of Reishi gathered, forming a brilliant blue spiritual bow and arrow.
Drawn to the limit, it fired!
The arrow let out a piercing shriek as it tore through the air, heading straight for the collapsed ruins.
Just as it was about to strike Sora, a familiar, undisguised voice suddenly rang out nearby.
"Bakudō #81: Danku."
An invisible, solid barrier descended from the heavens, blocking the arrow without any suspense.
The exploding Reishi splashed harmlessly against the Danku.
It didn't budge an inch.
Sora looked back in shock.
He saw a figure covered by a light-bending shroud step out from the darkness. A familiar brown, wavy hairstyle flickered for an instant before being covered by the Kidō glow again.
"Don't just stand there dazed."
The urgent voice rang in his ear. "The Seireitei is not suitable for us to fight at full power. Draw it to a secluded area in the Rukongai first."
"The mess here will be handled by the other Captains."
Despite the voice being disguised, Sora immediately recognized the identity of his savior.
In such a desperate situation, his "good brother" had actually risked exposing his identity to come to his aid. It was truly touching.
"Next time the prison cafeteria has a new tofu dish, I'll make sure to bring some to you first!"
"?"
'Is there something wrong with him?'
'Is now the time for such nonsense?'
Looking at the thumbs-up Sora gave him, Aizen felt his blood pressure spike.
A burst of Flash Step followed.
Sora seized the opportunity Aizen had created and bolted from the ruins, heading toward the edge of the Seireitei. He moved like a streak of light through the streets, vanishing in the blink of an eye.
Watching his departing back, Aizen narrowed his eyes.
'Has that brat's Flash Step gotten even faster?'
Just as Ukitake had said, the moment the creature sensed Sora's Reiatsu receding, it moved.
Its body melted into the shadows, racing toward the edge of the Seireitei like a dark flood.
Aizen gave one last look at Ukitake, who was vomiting blood in the ruins, took a deep breath, and vanished into the night.
District 9 of West Rukongai, the outskirts.
The monster formed from Soul King power moved quickly, catching up to Sora in no time.
As the heavy pressure returned, a blue Reishi arrow tore through the air.
Sora spun around and slashed the arrow apart, but when he looked back, he couldn't help but want to curse.
The twelve arms were working in pairs with clear division of labor, drawing bows and firing arrows. Reishi from the atmosphere was gathering frantically to form projectiles.
Then came a rain of light beams.
The air vibrated violently.
Sora didn't dare keep running. Leaving his back to an archer—especially one made of Soul King power—was a suicidal move.
The moment he turned, violent lightning exploded from his blade.
His blade swept out, the distorted arcs forming a sword pressure that savagely shattered the falling arrows.
Immediately after, Aizen arrived at the scene. From a great distance, he pointed a single finger.
"Hadō #90: Kurohitsugi!"
A black torrent surged from the ground. A long, coffin-like structure of iron walls instantly imprisoned the mutated Taketori.
Pitch-black blades erupted within, and the sound of tearing flesh was endless.
When the Black Coffin finally faded, a mangled, massive body emerged.
The shadows on the ground surged to meet it, repairing the gaps in its form in the blink of an eye.
Seeing this, Aizen's brow furrowed.
However, he soon noticed that although the creature looked intact, its Reiatsu was slightly weaker than before.
'If we keep up the attacks, we can eventually wear it down to nothing.'
Just as he was about to share his discovery with Sora, he noticed that not far away, pitch-black, materialized Reiatsu was billowing out like mist.
With no one else around, Sora stopped acting like a "noble hero."
He initiated active Hollowification.
A savage bone mask covered his face, and paired with a cruel grin, it was enough to make small children stop crying at night.
With a sharp crack, he moved.
Sonído.
Under Aizen's surprised gaze, Sora vanished from his spot.
Aizen couldn't even track the trajectory of his movement.
By the time Sora reappeared, he was right in front of the Soul King aggregate.
Sensing an enemy close by, the multiple eyes locked onto him. Twelve arms slammed down, threatening to crush him into a pulp.
Sonído dash, forward step.
Vajrayati swept out violently. The burning thunder and fire descended, instantly vaporizing the sludge-like shadows and brutally shattering the arms on the creature's flank.
Then, the blade plunged into the creature's chest like it was cutting paper and pulled!
Viscous black liquid sprayed out, soaking the earth.
Sora stared at the struggling monster, a hint of excitement flashing in his golden, slitted pupils as his black Reiatsu exploded without restraint.
"Take a deep breath and relax. It's normal to feel dizzy."
As he spoke, the brutal deconstruction began.
Shadows sprayed out like a geyser. Under the thunder-and-fire-cloaked Zanpakutō, the massive, mutated body quickly fell apart, the sound of tearing silk filling the air.
The Hollow power contributed by Arturo had pushed Sora's already strong Hollowification to a new level.
After actively entering this state, his raw stats had increased by another significant margin.
The heavy, sludge-like body had now become a liability. No matter how the monster tried to shift or writhe, it couldn't escape the crushing pressure.
Much less fight back.
With one merciless slash after another, limbs continued to shatter. The massive body instinctively tried to repair itself in a continuous loop until its immense Reiatsu finally collapsed entirely.
It could no longer hold its form.
The shadows dispersed, revealing the unrecognizable remains of Tsunayashiro Taketori.
Surprisingly, he was still alive.
His old, clouded eyes struggled to open, a gaze full of venomous resentment falling on the figure before him, as if trying to carve Sora's image into his soul.
Finally, with the descent of the blade, there was only silence.
Looking at the black sludge at his feet, Sora wiped the black blood from his cheek, a sense of accomplishment filling his heart.
'Justice executed!'
'Once again, I have saved the Soul Society from the brink of disaster!'