Under Aizen's leadership, Las Noches was thriving.
Sung-Sun's successful Arrancarification allowed the other Menos Grande to see the possibility of further advancement.
The Hollow population in Las Noches primarily consisted of Adjuchas, supplemented by Gillians, with only a very small number of exceptionally talented normal Hollows and animal Hollows that served as snacks or pets.
As intermediate Hollows, Adjuchas could generally achieve evolution by devouring their own kind or higher-level Hollows.
However, if they were ever bitten by a Menos Grande of the same level or higher, their evolution would permanently halt.
In an extremely unstable state, they might even regress into mindless Gillians, a process that was typically irreversible.
Therefore, for an Adjuchas, aside from basic survival, evolution was the main pursuit of their Hollow lives—one could even say it was their sole pursuit.
Now, the Prime Minister of Las Noches had personally announced the creation of an Arrancarification surgery that could allow Adjuchas to evolve.
Upon successfully becoming an Arrancar, their state would stabilize, eliminating the risk of regression.
Not only that, but their strength would multiply several times over, perhaps even tenfold.
And the price they had to pay was merely a trivial amount of physical pain and an almost negligible risk of the surgery failing.
How could the Hollows not go crazy over this?
Of course, Aizen, who preferred to stay behind the scenes and orchestrate everything, pinned all the credit on Naraku Sora.
As a result, the Adjuchas' loyalty to this new King of Hueco Mundo instantly reached its peak, leaving almost zero possibility of betrayal.
Coupled with the steady progress of Las Noches' renovation project, even some Menos Grande who had little desire for evolution gradually grew accustomed to life here.
They even faintly developed the absurd idea of wanting to protect this wonderful peace.
For instance, Tier Harribel.
"You're saying you want to participate in the second phase of the Arrancarification surgery?"
Naraku Sora looked at the shark-like monster girl in front of him with a face full of suspicion, momentarily wondering if she had been swapped with an imposter.
Harribel nodded calmly.
"My time living in Las Noches has made me realize that Soul Reapers are not all treacherous and wicked. They have their shining qualities as well."
"Although they are quite hard to find."
Naraku Sora: "?"
He suspected this woman was insulting him, and he had ample evidence.
"During my time in Las Noches, I have seen many things I had never seen before, things I had never even imagined."
Harribel's eyes softened slightly, and even her voice was no longer as icy.
"It turns out that Menos Grande can coexist peacefully. It turns out that Adjuchas can walk a path of evolution that doesn't rely on devouring their own kind. It turns out that we, too, can live peacefully under the moonlight..."
"And the one who brought all of this was not the former King of Hueco Mundo, but a Soul Reaper from the Soul Society."
"I must admit, my perspective was too narrow."
"Therefore, to thank you for the changes you have brought to Hueco Mundo, I am willing to pledge my loyalty to you, Lord Naraku."
Once upon a time, Baraggan had sent invitations to Harribel more than once, even dispatching his subordinate Adjuchas to hound and intercept her, all just to force her to become a member of Las Noches.
But as a Vasto Lorde, how could Harribel submit to him so easily?
Furthermore, from beginning to end, Baraggan had never once thought about doing anything for Hueco Mundo.
His purpose in recruiting Harribel was solely to strengthen Las Noches' forces, thereby further expanding his dominance over Hueco Mundo.
In contrast, how long had Naraku Sora been in charge of Las Noches? Yet he had already brought about earth-shattering changes.
Almost all the Menos Grande submitted to him wholeheartedly, and their cohesion was more than just a little bit stronger than before.
Most importantly, even though Naraku Sora possessed invincible power, he had never forced those Menos Grande to do anything from the very beginning.
Whether it was experiments or battles.
The Menos Grande had volunteered for all of them.
Submitting to such a King of Hueco Mundo didn't seem like a bad thing at all.
Given time, Naraku Sora would lead Hueco Mundo to greater heights, and Harribel believed that day was not far off.
Looking at Harribel kneeling on one knee before him to pledge her loyalty like a medieval knight, Naraku Sora scratched his head.
'Was I really that great?'
He hadn't expected even someone as stubborn as Harribel to surrender on her own initiative.
'Sure enough, compared to Aizen, my personal charisma is just a bit too strong.'
Thinking of this, Naraku Sora grinned and said,
"Since this is your sincere request, I will reluctantly agree."
"However, the risk factor for the second phase of the Arrancarification surgery is still a bit high. Wait for the third phase."
Harribel let out a soft breath and nodded.
"I understand, Lord Naraku. I will definitely work hard to protect this hard-won peace!"
As the collected data continued to be perfected, the Arrancarification project advanced steadily.
The bizarrely shaped creatures within Las Noches were gradually decreasing, replaced by "humans" wearing various masks.
Moreover, the overall architectural style was modeled after the Shino Prison.
Aizen directly brought out the blueprints he had designed previously, deleted some structures that were useless to Hollows, and applied them straight to Las Noches.
At present, more than half of it had already been completed.
It was worth mentioning that during this period, Grimmjow did not choose to undergo Arrancarification immediately. Instead, he continuously challenged the Menos Grande who had completed their Arrancarification.
The process was quite brutal, with both victories and defeats.
Most of the time, he was beaten to a bloody pulp.
The reason he made this choice was because Naraku Sora had told him that the difficulty of Arrancarification for an Adjuchas and a Vasto Lorde was different. Furthermore, once Arrancarification was complete, the difficulty of further evolution would skyrocket infinitely.
Most importantly, the power growth after Arrancarification in these two stages was also different.
In order to obtain even greater power, Grimmjow chose to evolve first and undergo Arrancarification later.
According to Aizen's deductions, for an Adjuchas to evolve, aside from meeting the most basic Reiatsu requirements, they mostly needed to fill the emptiness in their "hearts."
For a reckless brute like Grimmjow, who only cared about the thrill of battle, as long as his need for combat and slaughter was satisfied, he could steadily advance on the path of evolution.
This painful yet joyful life lasted for several months.
That was until Naraku Sora landed a punch, and the creaking sound of fracturing bones echoed from Grimmjow's body.
Immediately after, intense pain struck. His body twisted irregularly, looking like a sports car that had crashed into a guardrail at two hundred and forty miles per hour.
Instantly, his flesh tore open, and blood splattered everywhere. White bone fragments mixed with scalding blood, instantly dyeing the white panther red.
Despite his defeat, a trace of exhilaration surfaced on Grimmjow's face.
'Battling is so thrilling!'
A terrifying Reiatsu suddenly swept out, slamming into the faces of the spectating Hollows wave after wave like a surging tide.
The Adjuchas looked in shock at the figure crawling on the ground.
Amidst the intense light, his shattered body healed at a visible rate. His newly grown claws exuded a cold, icy gleam, as if they could slice through anything in creation.
Feeling the surging power within his body, the smile on Grimmjow's face grew increasingly ferocious.
'It's finally complete!'
'From today onward, I am also a top-tier Vasto Lorde!'
At this moment, boundless loyalty welled up in his heart.
Although he seemed rather brainless on a normal day, Grimmjow knew very well that without Naraku Sora patiently sparring with him, it would have been impossible for him to complete his evolution in such a short time.
When fighting other Menos Grande, he had to worry about accidentally killing them, but when fighting Naraku Sora, he didn't have to worry about that at all.
Moreover, even if he was severely injured, the newly built Hell Hot Springs in Las Noches could heal him in a short amount of time.
It could be said that his achievement today was entirely thanks to the great Lord Naraku!
Aizen watched Grimmjow's evolutionary process with great interest, occasionally jotting down a few specific frequency parameters in the notebook in his hand.
He was happy to see Naraku Sora's prestige in Las Noches growing higher and higher.
Firstly, it allowed for better control over these unruly and arrogant creatures.
Secondly, he could obtain a massive amount of experimental data and materials. Those Menos Grande were not only extremely cooperative, but they would even say thank you after the experiments were completed.
They were much more useful than the test subjects locked up in the laboratory.
Thirdly, it satisfied a certain someone's itchy hands and craving for a fight.
It was simply a win-win-win situation.
After completing his evolution, Grimmjow did not hesitate and immediately signed up for the next phase of the Arrancarification project.
The next day, a surging pillar of Reiatsu directly blew off the laboratory's metal roof and shot straight into the deep night sky, causing the entirety of Las Noches to tremble at his rebirth.
The Panther King was born!
His immense power gave Grimmjow an overinflated sense of confidence, and he immediately issued another challenge to Naraku Sora.
However, he soon learned exactly why the King of Hueco Mundo was Naraku Sora and not anyone else.
Even without drawing his sword, relying solely on a pair of indestructible iron fists, Sora still beat Grimmjow's laughable burst of power so badly that he couldn't tell up from down.
On this day, the Menos Grande once again gained a clear understanding of their King's true strength.
The King was the King because no Menos Grande was stronger than him.
Just as the number of Arrancars in Las Noches continued to increase, Ulquiorra suddenly sought out Naraku Sora.
"My King, I have a matter to report to you."
Naraku Sora, who was busy designing Arrancar uniforms, looked up blankly, staring at the person in front of him in confusion.
As early as the third phase of the renovation project, Ulquiorra had already completed his Arrancarification. He looked exactly as Sora remembered, except that under a certain someone's influence, his emotions were no longer so hollow.
Simply because he had found the meaning of his existence.
"You should remember that when we first met, my origins were mentioned."
Ulquiorra said respectfully, "I originally came from a clan of Menos Grande, but due to my uniqueness, I was ostracized by my peers."
"Later, in order to find the answers to certain questions, I chose to leave the clan."
"During my time in Las Noches, I suddenly realized that given the developmental potential of that clan, they will pose a threat to us sooner or later."
"Therefore, Lord Naraku, if you are willing, I would like to share detailed intelligence regarding the Black-Winged Great Demon clan with you."
Hearing this, Naraku Sora's eyes lit up, and he quickly pulled Ulquiorra to sit down.
"Tell me everything!"