Chakra is a very mysterious energy.
It possesses a versatility different from spiritual power, capable of simultaneously interfering with both matter and soul.
For a long time, Aizen Sōsuke has been deeply researching the limits of this energy.
However, due to his own temporarily shallow limits, despite countless attempts, he has not been able to fully grasp the operating principles of this energy.
Conducting Zanpakuto creation experiments was not only to increase his own power but also a starting point for touching the essence of this energy.
Just as exploring the essence of flame requires studying plasma, discovering the principles of electricity requires investigating the basic operation of electromagnetism.
It was precisely to study the deepest roots of Chakra that he thought of merging the three most ancient bloodlines: the god tree factor, Sharingan, and Byakugan.
Among these remaining two powers, the ultimate power of the Sharingan is what he currently has the best chance of accessing.
Uchiha Itachi was the 'candidate' he chose after countless considerations.
—Inner closure, fragile personality, outstanding talent, facing a desperate situation, contradictory and unable to extricate himself.
This was an excellent option.
The strongest bonds he possessed were limited to Uchiha Shisui and his limited family.
All Aizen Sōsuke needed to do was personally help him sever these bonds one by one.
Until finally, only he himself remained as an option.
The more one believes oneself to be fighting alone, the easier it is to be moved.
As long as this progresses step by step, Uchiha Itachi's Mangekyo Sharingan will be within his grasp.
Beyond that, compared to the power of the Mangekyo Sharingan itself, what Aizen Sōsuke was more concerned about was the microscopic changes that occurred at the Chakra level during the evolution from Sharingan to Mangekyo Sharingan.
Whether it was tirelessly escalating the conflict between the Village and the Uchiha Clan or finding opportunities to become Uchiha Itachi's 'life mentor,' it was all for this reason.
As long as the operating principles are mastered and the corresponding energy carrier is replicated, then even a Zanpakuto can use the power of the Mangekyo.
However, in this process, he appeared quite cautious.
The most superficial reason was his apprehension towards Uchiha Shisui.
Through various inquiries, he had already learned about the ability of this Mangekyo Sharingan wielder—Kotoamatsukami.
A Dōjutsu (Eye Technique) that can directly distort the thoughts of others.
For someone like Aizen Sōsuke, this was more terrifying than directly killing him.
Therefore, instigating a rift between Uchiha Itachi and Uchiha Shisui became a necessary process.
As for the deeper reason, it was Aizen Sōsuke's vigilance towards the truth of this world.
From a macroscopic perspective, the souls of the dead are also a form of energy.
In his previous life, the Soul Society was where souls went.
But in this world, souls suddenly disappear after a person dies.
What's more concerning is that these souls can be re-summoned through certain specific techniques.
So, where do the souls go?
Furthermore, what terrifying power do the 'people' who guard these souls possess?
Aizen Sōsuke did not delve into these thoughts, but instinctively remained wary.
After all, these were not questions he was qualified to consider at his current stage.
"Sōusuke-senpai?"
Just as he unconsciously fell into thought, the two of them had finished their noodles.
Uchiha Itachi seemed to have figured something out; his expression became firm and focused again, and he politely thanked him:
"Thank you very much for today."
"Your guidance has been of great help to me."
Listening to his words, Aizen Sōsuke's expression naturally shifted back to his usual gentle and amiable demeanor, and he calmly said:
"It is only right for a senior to guide a junior."
"I will also be pleased if Itachi-kun can come to terms with things."
"Also, sometimes you can talk about these matters with Clan Head Fugaku."
"I once worked with that person, and he is actually a very wise elder."
"It's just that he might not be very good at expressing himself."
Uchiha Itachi was startled: "Father...?"
"I understand."
After the meal was finished, Aizen Sōsuke stood at the street corner, quietly watching Uchiha Itachi slowly depart... "Itachi is back?"
"Did you eat out again today?"
When Uchiha Itachi returned home, his mother was clearing the dishes and turned to smile at him, looking somewhat relieved.
"Yes, with Mr. Aizen Sōsuke."
"Mr. Aizen? Ah, that very clever child." Uchiha Mikoto seemed to have some impression of him as well, smiling gently.
"Perfect, Father is teaching Sasuke a new Ninjutsu in the backyard right now, Itachi, you should go watch too."
"Sasuke has been training very hard recently."
As a mother, this simple, ordinary life seemed to be the most beautiful thing in the world for Uchiha Mikoto.
Uchiha Itachi nodded and moved to the backyard.
In front of the pond, Sasuke was struggling a bit to imitate his father's recent hand signs, trying hard to control his Chakra, with slightly red burn marks on both sides of his lips.
Getting burned on the mouth seemed to be the most common injury when learning Fire Release Ninjutsu.
'Will Sasuke end up with thick lips later?'
Uchiha Itachi thought to himself, for no apparent reason.
Perhaps hearing footsteps, little Sasuke, who had just been diligently memorizing hand signs, suddenly turned his head, and upon seeing his older brother return home, the serious expression on his small face immediately changed to one of joy:
"Onii-chan!!"
Uchiha Fugaku had already sensed Itachi's footsteps, but only now did he turn around, his hands still clasped as usual, his expression solemn:
"You're home?"
"Yes, Father."
Uchiha Itachi replied, while patting the head of little Sasuke, who had rushed to his side:
"Sasuke."
"Are you still practicing the Great Fireball Jutsu today?"
"I learned such a simple Ninjutsu a long time ago!" Little Sasuke grumbled with a pout, looking somewhat displeased, but then quickly brightened up, "Today Father taught me a new technique, the Phoenix Flower Jutsu!"
"That one is a bit difficult, isn't it?" Uchiha Itachi said, noticing his burned lips.
Although he had learned it after seeing it only once back then.
"Yes, you have to spit out fireballs many times!" Little Sasuke immediately perked up and chattered, "If you're not careful, you get burned, and my mouth hurts so much."
"If Sasuke wants to become a Ninja, he has to learn to endure this kind of pain, Ninja are very tough."
"I know that, of course!"
Uchiha Fugaku watched his two children, the older brother kind and the younger respectful, feeling somewhat comforted.
Even the hardships of the past few days seemed insignificant.
He thought, then looked at Itachi again.
His physical abilities and total Chakra volume had almost exceeded the Jonin level; it was time to teach him new techniques.
"Itachi."
"Have you mastered the Great Fire Annihilation Jutsu?"
Uchiha Itachi was startled; it seemed a long time had passed since his father last personally taught him, and after that, he had learned on his own.
However, he quickly reacted and shook his head:
"I haven't learned it yet, Father."
Uchiha Fugaku nodded, took out a scroll from his wide sleeve, and casually tossed it to him.
"Take a look yourself."
Uchiha Itachi was already accustomed to this teaching method; he just opened the scroll and looked at it twice, easily memorizing this Ninjutsu, which was considered top-tier even among B-rank techniques.
Tiger - Dog - Ox - Rabbit - Tiger.
Five hand signs were completed rapidly within one second.
The next moment, destructive flames, spreading like a torrent, erupted from the young man's mouth like a tsunami; the intensely rising scorching heat, even its aftershocks, made the skin of the two people nearby feel burning and their hair fly.
The wide pond in front rapidly evaporated under this high temperature; the forward-surging flame current, carrying an unimaginable impact, instantly dried up countless water vapor.
It gradually spread forward like an advancing city wall.
Finally, Uchiha Itachi actively cut off his Chakra supply, and this roaring city of fire gradually stopped.
Leaving only deep, charred marks on the ground.
Little Sasuke looked at this vast sea of fire, his eyes involuntarily widening, even his burned little mouth couldn't help but gape, his gaze fixed.
This, this terrifying power?
Is this a B-rank Ninjutsu?
Uchiha Fugaku, however, noticed Itachi's precise control.
Even in such a narrow place in the courtyard, he still accurately controlled the affected area of this difficult-to-manipulate giant Fire Release to be above the pond.
He didn't even ignite the wall less than twenty meters in front, completely grasping the key to this technique.
Uchiha Itachi looked back at him.
Fugaku, as steady as ever, nodded to him, a calm smile appearing on his solemn face:
"As expected of my son."