Regaining his composure, Sasuke began to assess his current situation, comparing his advantages over the Uchiha Sasuke of the same age.
1. Information: Foresight and Awareness
This point needs no further explanation; it remains his greatest advantage in this world.
2. Sharingan: Three-Tomoe Sharingan
When the original Sasuke witnessed the clan massacre, he had only awakened a single Sharingan eye—and even that was latent. It wasn't until the Zabuza Arc four years later, facing a life-or-death crisis, that he awakened the Sharingan to two tomoe.
Yet the current Sasuke, having experienced the same tragedy, awakened the Three-Tomoe Sharingan instantly and can activate and deactivate it at will.
Perhaps this is due to his two lifetimes of experience.
In his previous life, he possessed a natural aptitude for mental cultivation and over twenty years of adult development. After merging with Uchiha Sasuke's soul and body, he likely awakened the Three-Tomoe Sharingan immediately.
Of course, the physical shock of personally gouging out his parents' eyes may also have played a role, triggering dormant physical memory.
He now possessed a pair of Mangekyō Sharingan and a pair of Three-Tomoe Sharingan.
Both pairs were Sharingan from his closest blood relatives, ensuring he could at least evolve them into the Eternal Mangekyō in the future.
3. A talent similar to that of a Sensor Ninja.
This innate ability had been with him since his previous life. His body possessed an extraordinary sensitivity to visual perception, which had been amplified even further after merging with this new body.
In his past life, he had needed to stare intently at security cameras to barely detect whether someone was watching him.
Now, even without direct eye contact, Sasuke could instantly sense the Third Hokage spying on him through the Crystal Ball, which was far more covert than any camera.
However, unlike Sensor Ninjas, who could use Chakra to perceive flows, positions, and movements within a radius of kilometers, or even hundreds of kilometers, Sasuke's perception was purely visual.
While he lacked the broad range of a Sensor Ninja, it remained an invaluable asset, guaranteeing he wouldn't be caught off guard by spies or ambushes.
After a rough assessment, Sasuke concluded he had only these advantages over the original owner of the body.
Having possessed this body for less than five days, and excluding the Sharingan, his mastery of ninjutsu and taijutsu in his base state was no better than the original owner's—at least for the time being.
Having summarized his current situation, Sasuke walked to the desk, picked up a pen, and prepared to make a simple plan.
'How can I rapidly increase my strength?'
'What is my immediate goal?'
After posing these questions to himself, Sasuke wrote down two sentences in English:
'Mangekyō Sharingan, Eternal Mangekyō!'
Without a doubt, with the Mangekyō Sharingan of his father, Uchiha Fugaku, now in his possession, his most crucial objective—and the fastest path to power—was to transplant his father's Mangekyō Sharingan and evolve it into the Eternal Mangekyō.
To achieve this goal, Sasuke faced two critical challenges:
His own Sharingan needed to evolve into the Mangekyō Sharingan before transplantation was possible.
He needed to either learn Medical Ninjutsu or find someone he trusted to perform the transplant surgery for him.
As Sasuke gazed at the words on the paper, his eyes narrowed slightly as he sank into contemplation, pondering how to resolve these two challenges.
First, let's address the Mangekyō Sharingan.
In the original narrative, the advancement condition for the Mangekyō Sharingan was: "To understand love and then lose it."
When an Uchiha who had experienced profound love lost that intense affection, their love would be replaced by an even stronger hatred.
The excruciating pain would then trigger the release of a special Chakra within their brain, which would act upon their optic nerves, causing their eyes to transform and evolve into the Mangekyō Sharingan—eyes that reflected the depths of the soul.
Of course, there was also a prerequisite: the Uchiha who understood love and lost it must possess exceptional latent mental talent.
At this point, Sasuke thought of Uchiha Obito and added a note: 'This talent should be divided into latent and manifest forms.'
Immediately after writing this, Sasuke frowned as he reread the conditions for unlocking the Mangekyō Sharingan.
His current body's innate talent was far from lacking; in fact, it could be considered exceptional.
After all, he was one of the protagonists, and after merging with this vessel, his mental capabilities had been significantly enhanced.
'But to understand love, then lose it?'
Sasuke shook his head inwardly. Even when his parents died before his very eyes, he hadn't awakened the Mangekyō Sharingan under such intense emotional shock.
Moreover, he could sense that he was gradually mastering this body, and the influence of those memories was diminishing.
Now, when he recalled that night's scene, he no longer felt the overwhelming grief that had once consumed him.
At this rate, even if Uchiha Itachi died at his hand as in the original story, Sasuke might still fail to meet the conditions of "understanding love" and "losing love."
Even if he could meet those conditions, Sasuke had no desire to replicate the original story's final battle—a heavily rigged farce where he was spoon-fed victory and manipulated at every turn, all to awaken the Mangekyō Sharingan in a preordained manner.
Looking back at his predecessor's life, Sasuke realized it had been nothing but a series of manipulations and deceptions orchestrated by others—Orochimaru, Uchiha Itachi, Uchiha Obito, and Uchiha Itachi... again.
After finally gaining supreme power, he discovered he was merely the reincarnation of some chakra will, a pawn in the grand design laid out long ago by the Sage of the Six Paths.
Now that he was the master of this body, he refused to follow anyone else's plans, regardless of whether they claimed to be good or evil.
'Do you really think you can control everything?'
'My life is mine to decide. If I do something, it's because I want to, not because you arranged it.'
'Hah.'
At this thought, Sasuke's gaze deepened.
His mind raced, sifting through countless fragments of knowledge from his previous life's understanding of the original manga in mere breaths, seeking a solution to his stalled Mangekyō advancement.
In the manga, the Sage of the Six Paths, founder of the ninja world, possessed the Rinnegan in both eyes from birth, along with a third eye resembling the Eye of the Moon on his forehead.
The Rinnegan was considered an evolution of the Mangekyō. In the anime, the Sage of the Six Paths awakened his Three-Tomoe Sharingan in response to intense trauma, immediately followed by the Rinnegan.
However, the manga depicted him with the Rinnegan from birth, without any triggering event.
'If I use the manga as a reference...'
The Sage of the Six Paths' innate Rinnegan stemmed purely from his pure bloodline and naturally immense Mental Energy.
The Uchiha method might merely be one path to achieving the Mangekyō—a drastic increase in Mental Energy triggered by intense emotional trauma, leading to a qualitative shift in ocular power, a sudden leap to transcendence.
If he couldn't attain the Mangekyō through this shortcut, perhaps he could accumulate Mental Energy gradually, like drops forming a river and then a sea, increasing the quantity steadily until it triggers a qualitative transformation.
Even if things didn't go as planned, increasing his Mental Energy would only benefit him, never harm him.
With this thought in mind, Sasuke wrote down "Increase Mental Energy" on the paper, adding a few lines below:
• Hone willpower.
• Accumulate experience.
• Meditate and cultivate.
These were the three methods he could think of for mental cultivation based on his current knowledge.
Of course, beyond these, he would also search the Uchiha Clan's records for any techniques to enhance mental energy.
Having formulated an approach to the first challenge, Sasuke turned his attention to the second—Medical Ninjutsu!
Sasuke's current body wasn't a Sage Body like Uchiha Madara's, so he couldn't simply switch between his Sharingan and Rinnegan at will.
Therefore, he needed to master Medical Ninjutsu.
Based on his memories, the Ninja Academy didn't offer dedicated Medical Ninjutsu courses, only basic pharmacology and first aid knowledge.
After all, mastering Medical Ninjutsu required exceptionally high qualifications:
A thorough understanding of human anatomy.
Exquisite Chakra control.
Mastery of Yang Release Chakra!
Hashirama Senju, the founder of Medical Ninjutsu, developed a special technique to infuse patients with the life force of Yang Release Chakra, stimulating cellular regeneration to heal wounds.
By manipulating its form, he could also create antidotes and launch offensive strikes.
While Yang Release Chakra might sound advanced, it's actually quite common. The Akimichi Clan's Human Boulder Technique is a form of Yang Release Ninjutsu, and Medical Ninjutsu itself is a branch of this discipline.
What's truly advanced is the Six Paths Yang Power, not Yang Release itself.
The Uchiha Clan inherited the Sage of the Six Paths' Yin Power, but that doesn't mean Sasuke can't develop the Yang Release Attribute.
Yang Release Chakra is essentially life force, and in some ways includes the Physical Energy that composes Chakra.
The Uchiha Clan's Physical Energy may appear weaker compared to the Senju and Uzumaki clans, but it far surpasses that of most other clans.
'I wonder if my Yin Release Chakra will suppress Yang Release, preventing me from mastering the Yang Release Attribute,' Sasuke pondered internally.
As far as he could recall, the official character databooks never listed Yang Release as one of his attributes, even by the final battle.
Setting aside the third point for now, Sasuke focused on mastering the first two.
Even if he never fully mastered Medical Ninjutsu, by that point, he would possess enough medical skill to perform an eye transplant on himself.
After writing it all down, Sasuke summarized his goals:
Increase his Mental Energy.
Master Medical Ninjutsu, at least enough to perform an eye transplant on himself.
After mentally reviewing the details of his plan, Sasuke burned the paper.
"Who keeps a diary these days?" he muttered sarcastically. Even though the text was written in English, there remained the risk of it being deciphered. Ever cautious, Sasuke destroyed the evidence.
With everything taken care of, Sasuke stripped off his clothes and climbed into bed, ready to rest.
'I already missed the school exams while I was unconscious. This two-month break at the clan compound means I can skip school—that saves me some trouble.'
'Tomorrow, after I wake up, I'll see if I can find any useful technique in the Uchiha Clan.'