When a human dies, their soul does not immediately vanish.
Instead, they become a Plus.
At that moment, a chain appears attached to the chest of the soul.
This chain is known as the Chain of Fate (Inga no Kusari).
The condition of the Chain of Fate reflects the state of the soul itself.
If the soul remains stable, the chain remains intact.
However
If the soul is consumed by intense emotions such as regret, hatred, or obsession, or is influenced by external spiritual forces, the chain begins to erode.
There are two primary outcomes when this process unfolds.
First
If the chain is forcibly destroyed, the soul may completely collapse and disperse.
But more commonly
The chain gradually corrodes.
As the Chain of Fate shortens and decays, a hollow void begins to form at the chest.
Eventually
The chain disappears entirely.
And in its place
A hole is born.
That hole is the defining mark of a Hollow.
Even an ordinary Plus with no spiritual power can transform into a Hollow under these conditions.
Once transformed, the being is no longer governed by reason.
It becomes driven purely by instinct
To devour.
Hollows prey upon souls.
Especially in the World of the Living, where unprotected Pluses are abundant.
Even the weakest Hollow can cause devastating damage to both souls and spiritually aware humans.
For this reason
The duty of the Shinigami is clear:
To maintain the balance of souls.
While destroying Hollows through purification is one method
There exists a far more efficient approach:
Prevent their creation altogether.
That method is known as Soul Burial (Konsō).
By performing Konsō, a Shinigami sends a Plus safely to Soul Society, preventing the degeneration into a Hollow.
It is a fundamental technique.
One that every Shinigami must master.
Each year, the Shin'ō Academy arranges practical training exercises in the World of the Living.
Students are sent in supervised groups to perform Soul Burial under the guidance of an instructor.
Even if many of them will never be assigned to the Human World after graduation
This skill is considered essential.
Among this year's students
Several stood out.
Abarai Renji.
Kira Izuru.
Hinamori Momo.
Though each had their own strengths and weaknesses
For example, Renji's poor aptitude in Kidō
Their overall performance placed them among the top of their class.
However
During this routine training mission
Something went terribly wrong.
A Hollow appeared.
But this was no ordinary Hollow.
Its Reiatsu was abnormally dense.
Its movements were precise.
Its presence alone overwhelmed the surrounding area.
The moment it appeared
Students began to die.
Panic spread instantly.
Even those with combat training were unable to respond effectively.
The instructor leading the group
A seated officer from the Thirteenth Division
Immediately engaged the Hollow.
But the result
Was decisive.
He was killed.
In the face of such overwhelming power
The remaining students were pushed to the brink of annihilation.
And then
At the very moment despair reached its peak
A figure appeared.
Like a savior descending onto the battlefield
Captain of the Fifth Division—Aizen Sōsuke.
Behind him stood his lieutenant
Ichimaru Gin.
With calm composure and a gentle expression
Aizen stepped forward.
The battle ended almost instantly.
With a single, effortless strike
The Hollow was purified.
The oppressive Reiatsu vanished.
Silence returned.
The surviving students stared in shock.
Relief.
Admiration.
Awe.
That moment engraved itself deeply into their memories.
For Renji
For Izuru
For Hinamori
The image of Aizen Sōsuke became something unforgettable.
Not far from the site of the incident
In an inconspicuous area of the Human World—
Stood a small shop.
Urahara Shop.
Over the years, Urahara Kisuke had firmly established himself here.
The operation ran smoothly.
Quietly.
Without drawing attention.
The Visored victims of Hollowfication did not reside here.
After gaining control over their Hollow powers, they chose to live independently.
Thus, within the shop remained:
Urahara Kisuke
Shihōin Yoruichi
Tsukabishi Tessai, former Captain of the Kidō Corps
Yoruichi often appeared in the form of a black cat, masking her identity.
Tessai, once a high-ranking master of Kidō, now handled mundane shop duties cleaning, organizing, assisting customers.
The contrast from his past was stark.
Whenever Gosuke Shigure visited
He could not help but feel a sense of irony.
The proud former leader of the Kidō Corps
Reduced to a shop assistant.
At this moment
They were observing the Soul Burial incident from afar.
Thanks to Tessai's advanced barrier techniques and Urahara's spiritual concealment devices
Their presence remained completely hidden.
Even from Aizen.
"That Hollow…"
Gosuke Shigure spoke quietly, his gaze distant.
"…was created by Aizen."
He had sensed it immediately.
"In truth, I could have intervened earlier," he added calmly.
"But since Aizen was already present… there was no need."
Urahara adjusted his hat slightly, his usual relaxed demeanor replaced by rare seriousness.
"So you noticed it too."
He continued:
"Aizen and Ichimaru didn't 'arrive in time.'"
"They were already there observing."
"This was an experiment."
Gosuke said nothing.
But his silence confirmed it.
"As you warned us before," Urahara went on,
"Aizen has begun shifting his focus toward Hollows."
"Over the past years, Shinji and the others explored Hueco Mundo."
"And what we found…"
He paused briefly.
"…was something unprecedented."
"Arrancar."
Beings that blurred the boundary between Hollow and Shinigami.
"When a Shinigami undergoes Hollowfication, their power increases dramatically," Urahara explained.
"Likewise, when a Hollow removes its mask crossing that boundary it can also evolve."
"Ordinarily, breaking a Hollow's mask would lead to its destruction."
"But Aizen…"
"He has found a way to stabilize that process."
"To create Hollows that do not die when their masks are broken."
"To create Arrancar."
Gosuke's eyes narrowed slightly.
Urahara's voice grew heavier.
"The stronger the Hollow, the greater the result after becoming an Arrancar."
"And those with unique abilities…"
"…grow even more dangerous."
He exhaled slowly.
"Based on our findings…"
"Hueco Mundo…"
"…has already fallen under Aizen's control."
Silence settled in the room.
This conclusion had been reached long ago.
But stating it aloud
Made it real.
Aizen was no longer acting alone.
He now possessed an army.
And not just any army
But one composed of evolving Hollows that defied the natural order.
"Which brings us back to this incident," Urahara said.
"That Hollow earlier…"
"…was likely an artificial creation."
"A prototype."
"A deliberately engineered subject designed to test stability, strength, and control."
Gosuke Shigure closed his eyes briefly.
Aizen was accelerating.
The timeline
Was moving forward.
And the war that had yet to begin
Was already taking shape in the shadows.
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