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"Roar—"
A bizarre, ear-splitting shriek echoed, filled with wails.
Standing inside the immensely vast cavern, Tier Harribel's expression was somewhat strange, and the incessant wailing made her feel uneasy.
She had saved a Shinigami…
If that were all, it would be fine.
But while saving a Shinigami, she was also constantly capturing her own kind to be studied by him. Of course, she didn't feel guilty, nor did she have any sense of 'the fox grieving for the dead rabbit'.
After all, Hollows inherently devour each other.
In Tier Harribel's eyes, those Hollows with questionable or even non-existent intelligence were merely snacks and tools.
Whether Hollows lived or died was irrelevant, but helping a Shinigami research Hollows—no matter how she thought about it, she felt it was deeply problematic.
Especially…
The increasingly fanatical expression on Ishikawa's face made her uneasy. After half a month, she felt that his gaze towards her was becoming more and more dangerous, as if he wanted to study her from the inside out.
I'm just doing this to become stronger, so I can be of more help to that Lord.
Tier Harribel kept repeating this in her mind, as if trying to convince herself.
"Awooooh~"
The screams gradually weakened until they vanished.
Ishikawa stared intently at the Gillian slowly dissipating before him, a contemplative look in his eyes.
"Did you gain anything?"
Tier Harribel's voice broke Ishikawa's contemplation. He shook his head slightly: "You could say yes, but you could also say no."
It was impossible to research a method for Arrancar evolution within half a month.
No matter how comprehensive the knowledge granted by the system in Ishikawa's mind, researching new life forms was an extremely difficult task, so Ishikawa didn't aim too high.
In the past half month, his research direction wasn't how to evolve Arrancar, but rather to find the direction of Arrancar evolution.
Arrancar can also be described as the Shinigami-fication of Hollows.
Regular Hollows, Gillian, Adjuchas, Vasto Lorde… any Hollow could break through the upper limit of their life stage by becoming an Arrancar, thereby gaining a Shinigami's Reiatsu, allowing their Hollow Reiatsu to mix with the Shinigami Reiatsu, and both would be further strengthened.
After becoming an Arrancar, Hollows gain a Zanpakuto similar to a Shinigami's, but unlike a Shinigami, an Arrancar's Zanpakuto is essentially a sword-form of a part of the Hollow's own power, sealed by the Arrancar's 'soul core'. Therefore, an Arrancar's Zanpakuto abilities are often related to its abilities when it was a Hollow, merely evolved as its life stage increased.
Thus, an Arrancar's sword release is also called Release Form; upon release, they can unleash their full power and return to their true Hollow form, which can also be said to be their most suitable combat form.
However, the true form returned to after Release Form is not the form of the 'Hollow' before becoming an Arrancar, because whether it's a regular Hollow, or a Gillian, Adjuchas, etc.… after they become Arrancar, their Release Form still appears humanoid, rather than completely reverting to their various forms before becoming an Arrancar.
And the problem lies here.
A Shinigami's sword release allows them to use various Zanpakuto abilities and increase their own Reiatsu, serving as a method to enhance combat power.
However, an Arrancar's Release Form is about releasing their sealed power, meaning this power was already possessed by the Hollow after becoming an Arrancar; it was merely in a sealed state normally.
Taking Tier Harribel, whom Ishikawa is most familiar with, as an example: before becoming an Arrancar, she was an Adjuchas with a bird-like appearance, not particularly strong, roughly comparable to a weaker Vice-Captain.
After becoming an Arrancar, breaking through the limit barrier not only raised her upper limit but also forcibly raised her lower limit due to the integration of Shinigami Reiatsu; even in her current normal state, possessing both Shinigami and Hollow Reiatsu, she has the Reiatsu intensity of a top Vice-Captain-level.
After Release Form, she can further increase her Reiatsu proficiency by approximately 100,000 to 200,000, instantly becoming a Captain-level existence.
Forcibly often implies harm.
According to Tier Harribel, including herself, most Adjuchas have an evolution limit, and becoming an Arrancar is a way to forcibly break this limit; after forcibly breaking the limit, while strength certainly increases significantly, it doesn't mean the evolution limit is gone forever. Instead, as mentioned earlier, it's merely raised.
Moreover, because it was forcibly broken, combined with an imperfect method of breaking, her upper limit became even more insurmountable, making further evolution impossible.
Although it's just a guess…
Ishikawa has a feeling that when Aizen obtained the complete Hōgyoku, the reason he abandoned the original Espada, which he had completely researched and created himself, was very likely because the imperfect method of breaking the limit caused these original Espada to completely lose the possibility of evolution.
Tier Harribel has already encountered her limit again; to increase her strength, she can only continue to evolve; and if Ishikawa's guess is true, it means she has lost the possibility of evolution.
Therefore, breaking through the life stage barrier again to further raise her upper limit is impossible, because when she first became an Arrancar, she no longer had a 'barrier'; it could also be said… her current form is her ultimate life form, and for her, there is no such thing as breaking the 'upper limit of life form'!
Aaroniero Arruruerie.
The reason he, also one of the original Espada, was not eliminated was precisely because his abilities allowed him to continue to gain strength even in his 'ultimate life form'.
What he meant by 'infinite evolution' was not evolution in 'life form', but rather evolution in strength through his own abilities.
As for the other eliminated Espada, they didn't even possess the possibility of 'strength evolution'. As the Arrancar-fication technique improved, it was perfectly normal for them to be eliminated!
What Aizen couldn't do, Ishikawa naturally couldn't do either.
So, at the beginning of his research, he abandoned the path of 'life form evolution' and instead focused on researching the possibility for Tier Harribel to achieve 'strength evolution' in her 'ultimate life form', similar to Aaroniero.
And this possibility was precisely the Development Spiritual Mark, created by the system's deduction after Ishikawa established a tiny bit of feasibility.
His Development Spiritual Mark is a technique that acts on the Spirit Core, forcibly increasing the efficiency of the Spirit Core in converting its own Reiatsu. It feels somewhat similar to the cultivation methods in those wuxia novels, allowing his Reiatsu to increase much faster than a normal Shinigami.
Although Hollows do not have the Spirit Core found within a Shinigami's Spirit Body, Arrancar do possess a 'soul core' after becoming Arrancar. This soul core is identical to the Spirit Core; it is also the core of Reiatsu, also the energy source that sustains life, and likewise, damage to it results in instant death…
It can be said that although the two differ in form, their function is completely identical. One is the core of a Spirit Body, the other the core of a Hollow body, differing only in the nature of their Reiatsu.
This indicates that the Development Spiritual Mark could very well act upon the soul core, thereby allowing Tier Harribel, who has already lost the potential for growth, to achieve a further increase in Reiatsu.
But before that, the nature of the soul core needed to be fully understood.
The reason Ishikawa was able to create the Development Spiritual Mark… even if it was just a sliver of feasibility, was entirely due to his contact with and research of numerous spiritual bodies.
The ordinary people of Rukongai, the prisoners of the Maggot's Nest, the patients of the Comprehensive Relief Station… all combined, there were at least tens of thousands of them, which allowed him to create even that tiny bit of possibility.
However, ordinary Hollows do not possess a 'soul core'; only Arrancar do. Therefore, no matter how many Hollows Ishikawa researched, he couldn't fully understand the nature of the soul core.
But he could only deduce the formation method and structure of the soul core by studying Hollows. The reason is simple…
There were simply too few Arrancar!!
In the past half month, at his request, Tier Harribel, under the pretext of 'being offended', captured some subordinates or Arrancar test subjects in Las Noches, but there were fewer than ten in total.
Even though Ishikawa treated these rare test subjects very carefully, the longest any of them survived was only three days.
Fortunately, through his alternating research on Hollows and Arrancars, he had gradually gained some insight.
Although he really wanted Tier Harribel to return to Las Noches to capture a few more Arrancars... capturing ten Arrancars in half a month had already caused dissatisfaction among the other Arrancars. Fortunately, when Aizen and his two companions were not in Las Noches, such incidents were common, so no one suspected that Tier Harribel's capture of Arrancars had an ulterior motive.
However, continuing to capture them like this would inevitably attract attention, though the attention of Arrancars themselves was not so bad. But being targeted by the actual Boss of Las Noches would be problematic.
Although...
Ishikawa felt that the news of his presence in Hueco Mundo and his engagement in battle with the Espada had probably already reached that individual's ears.
Every time he thought of this, Ishikawa couldn't help but feel uneasy.
Although the Seireitei seemed to have some understanding of Arrancars, the existence of the 'Espada' was a secret. Who knew if that individual would, to prevent Ishikawa from reporting information about the Espada to the Seireitei, keep him in Hueco Mundo forever, or... simply eliminate him when he left Hueco Mundo and returned to the Human World or Soul Society.
So, if he didn't report it, would there be no problem?
No...
Because he couldn't possibly run up to Aizen and tell him, 'I know the Espada are your subordinates, and I swear I will never disclose information about the Espada to the Seireitei.' Doing so would either get Ishikawa directly killed or force him to find a way to become Aizen's lackey.
And not seeking Aizen, and simply not reporting his experiences in Hueco Mundo to the Seireitei to avoid Aizen's hostility, was even more impossible.
Because Aizen couldn't possibly be unaware of the news of his battle with the Espada. Given that individual's personality, if Ishikawa didn't speak, he would instead suspect if Ishikawa had discovered something or had some secret plans. In that case, Ishikawa's fate would be the same as above.
Therefore, after Ishikawa returned, he absolutely had to report his experiences in Hueco Mundo and the existence of the Espada. Doing so was not for the Seireitei, but for Aizen... although that sounded a bit strange.
For Ishikawa, the best outcome would be if Aizen simply didn't care about the Seireitei knowing the Espada's information; after all, Ishikawa had only overtly encountered two Espada.
As for whether this would expose Aizen as the 'King' of Hueco Mundo, there was no need to worry at all.
Because of the existence of Las Noches...
The Seireitei actually always knew, and was very clear, that the King of Las Noches was Baraggan Louisenbairn. Even now, the 'King' of Hueco Mundo on the surface has not changed. Many Hollows don't even know that their 'King' is no longer the one seated on the throne of Las Noches.
So, upon learning of the Espada's existence, the Seireitei would only assume that the Espada were gathered by Baraggan from various parts of Hueco Mundo.
Generally speaking, to avoid suspicion, the last possibility is the highest.
After all, if Ishikawa was killed outside immediately after leaving Hueco Mundo, some intelligent people in the Seireitei would inevitably suspect if someone within the Seireitei didn't want Ishikawa to bring back certain information.
But killing Ishikawa within Hueco Mundo could avoid such trouble.
For safety, Ishikawa had concealed all his aura during this period and had set up various Spiritual Crests within this cave, using Tier Harribel's Spirit Core as the core, for sound insulation, vibration reduction, and odor elimination... Furthermore, while Tier Harribel was out, he had opened up several secret passages.
It could be said that as long as Tier Harribel didn't betray him, even if Aizen himself came looking, Ishikawa would be able to escape completely.
Although the consequences of battling an Espada made Ishikawa uneasy.
But...
No regrets!!
Regarding the battle with Aaroniero itself, Ishikawa had no regrets, even when he was fully conscious.
In the past, every time he added experience points to attributes other than Spirit Core, Ishikawa would feel immense regret afterward. Only this time, he only regretted not killing Aaroniero with his final blow.
...
"Are you really capable of this?"
Tier Harribel looked at the frowning Ishikawa, her expression somewhat complex, and said, "And..."
After a moment of hesitation, Tier Harribel swallowed the rest of her words. She had originally wanted to ask, 'As a Shinigami, why are you helping me increase my strength?' But when the words reached her lips, remembering their half-month of interactions, she didn't know whether she should ask anymore.
Because...
For the past half-month, he had truly been searching for ways to help her improve her strength.
He even, to put her at ease, without her asking, repeatedly self-harmed, slowing down the healing of his own injuries, making his life completely within her grasp.
And as their time together grew longer, he seemed to trust her more and more, and the self-inflicted injuries became increasingly severe, as long as they didn't affect his mobility.
(I will definitely make you stronger!!)
Every time he said this, his expression was incredibly resolute, incredibly sincere, without any pretense, as if he had made it his lifelong goal.
"Don't worry."
A gentle voice, paired with a warm, sun-like smile, his eyes filled with determination: "I've found the direction. I will definitely make you stronger!"
"Hmph—"
Tier Harribel turned away with a displeased look, snorting, "You'd better be able to do it." With that, she turned and walked out, saying as she went, "Not long ago, a Gillian in the Forest of Menos evolved into an Adjuchas. It's been under my surveillance, and I'll bring it to you."
Adjuchas?
Ishikawa's eyes lit up. He had dissected many ordinary Hollows and Gillians, but Adjuchas were rare, and Ishikawa hadn't studied many of them yet.
Moreover, its life form had just evolved, which could be of great help to his research!
Ishikawa had a premonition that the moment he deciphered the Arrancar's 'soul core,' his research results would very likely appear on the system interface, thereby allowing him to acquire the abilities of Hollows; and it wouldn't be by merging with a Hollow, but simply by a Shinigami life form using abilities only possessed by Hollows!
It could be called...
The evolution of the Shinigami life form!
[Tier Harribel's Favorability +1, gained 2400 experience points. Current Favorability: 30]
30 points, huh.
Looking at the prompt on the system interface, Ishikawa nodded inwardly.
Although she still acted aloof towards him, she had already come to regard him as a very close friend. It could be said that even if he proposed leaving now, she probably wouldn't stop him.
But...
Ishikawa now didn't want to leave.
Current Experience Points: 23100
30 points of favorability had already provided him with nearly twenty-five thousand experience points. If his research succeeded, Tier Harribel's favorability towards him would very likely reach max friendship; by then, she would become Ishikawa's first Captain-level confidant.
The experience points gained from each point of her favorability increase were the same as Kukaku's. Ishikawa had calculated the experience points he could gain from max friendship.
The result was...
198300 experience points!!
And this was calculated based on Tier Harribel's current strength. If he further improved her strength, the experience points gained would likely be even higher than Ishikawa's calculation!
Whether for experience points or to gain Hollow abilities.
Ishikawa had no intention of leaving Hueco Mundo, even if Aizen himself came to drive him away... Such a high amount of experience points was enough for Ishikawa to choose to take a risk!
Moreover, to avoid being targeted after returning, Ishikawa had to store a certain amount of experience points to prevent various situations from occurring.
However...
Ordinary self-harm was already difficult to increase favorability, and Ishikawa was hesitant about whether to increase the degree of self-harm even further.
Anyway, his self-harm was controlled; in his current state, about ten thousand points of physique addition could restore nearly half.
As long as the degree of self-harm remained within the consumption of twenty thousand experience points, Ishikawa had no need to worry about losing combat ability because of it.
Moreover, the good fortune of being able to increase favorability just by self-harming was, in Tier Harribel's case, truly unique!
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