Naruto: Blade of the Sharingan

Within a cave, Uchiha Nagi and Kimimaro had found a place to rest.

Uchiha Nagi took out dry rations and water, handing them to Kimimaro. At the same time, he retrieved several test tubes and began to mix some dyes.

"Lord Nagi, what are you doing?" Little Kimimaro asked curiously.

"Your white hair is too conspicuous. It needs to be dyed black to make it easier to avoid detection. After I've completed my deal with Orochimaru, I'll take you away from the Land of Water and show you the vast world outside."

"Oh~"

"By the way, you don't need to call me 'Lord' in the future. I don't really like being addressed that way," Uchiha Nagi said. Although 'Lord' or 'Master' wasn't particularly special in the ninja world, merely a sign of respect, Uchiha Nagi just didn't care for it; it felt too much like a rigid class distinction.

Kimimaro scratched his head, puzzled. "Then what should I call you?"

Uchiha Nagi pondered for a moment. Big Brother? Adoptive Father? No, best not.

"Call me Sensei from now on."

Uchiha Nagi felt that rather than establishing a hierarchical relationship like big brother, adoptive father, or lord, it was better to simply be student and sensei.

There was a saying: A teacher for a day is a father for a lifetime. Orochimaru had taken Kimimaro in, viewing him as a vessel, but who knew if there were any genuine feelings involved? After all, Orochimaru couldn't even bring himself to kill Anko, who had attempted to kill him, her former master. How much more hesitant would he be with Kimimaro, who was fiercely loyal and whom he had raised from a young boy?

In the original timeline, Kimimaro had respectfully called Orochimaru 'Lord Orochimaru,' which seemed like a master-subordinate relationship, but in reality, it was perhaps more akin to that of a master and disciple. When Kimimaro died, Orochimaru had shown a flicker of uncharacteristic emotion, though it was buried very deep.

Wait, Sensei…

Uchiha Nagi suddenly remembered that people in the ninja world had a habit of killing their teachers. Orochimaru killed the Third Hokage, Nagato killed Jiraiya, and Sasuke killed Orochimaru.

He shook his head vigorously. Kimimaro shouldn't be that kind of person. If he properly instilled in him the concept of respecting one's sensei and valuing the Way, it probably wouldn't happen. Probably…

"Kimimaro, what ninjutsu do you currently know?" Uchiha Nagi asked.

"What I know? Hmm, from my clan's Shikotsumyaku, I only know a part of it. Ten-Finger Drilling Bullets, and this bone blade, as well as creating chakra bones beneath my skin. That's all…" Kimimaro thought for a moment before replying.

He was still just a boy; his body hadn't fully developed yet. Knowing this much was already quite remarkable. Simply being able to create hardened chakra bones beneath his skin made him a human tank.

As for the Ten-Finger Drilling Bullets, due to his current age, its power was still quite weak, about the same as throwing a kunai.

"Do you not know any other ninjutsu? For example, the Three Basic Jutsu, or elemental ninjutsu?" Uchiha Nagi inquired.

"I'm sorry, Sensei, I don't. The clan head didn't teach me…" Kimimaro scratched his head, embarrassed.

"From today onwards, unless your life is in danger, do not use the power of the Shikotsumyaku. Later, I will teach you the Three Basic Jutsu and other ninjutsu. Remember, unless it's a life-or-death situation, absolutely do not use the power of the Shikotsumyaku," Uchiha Nagi said to Kimimaro seriously.

The power of the Shikotsumyaku was immense. When Kimimaro was with Orochimaru, he looked down on other ninjutsu because this power was so overwhelming. This led to him becoming incredibly strong later on, even personally taking down Gaara's father, the Kazekage. But the result was the Kekkei Genkai disease—the genetic illness of the Shikotsumyaku—worsening, and then he… expired.

Uchiha Nagi hoped Kimimaro would reduce the development of his Shikotsumyaku, thereby delaying the onset of his body's Kekkei Genkai disease, or perhaps even see if it could be cured.

"Uh, yes, Sensei. But why don't you want me to use it? My Kekkei Genkai's abilities are very strong and useful," Kimimaro asked curiously.

"Overdeveloping it will trigger the genetic disease within your body. I will teach you other things in the future. In short, do not use the Shikotsumyaku unless you are facing mortal danger."

"Oh."

The current Kimimaro was a polite young boy. Although he didn't understand what a 'genetic disease' was, he knew this sensei was concerned for him, and a warm feeling instantly spread through his heart.

Kimimaro happily took the dry rations and heated them over the campfire. He also proactively spread out the bedsheet, clearly in a very good mood.

After they had eaten and drunk their fill, Uchiha Nagi picked up the dye and colored Kimimaro's hair black, making him less conspicuous.

"Sensei, the bedsheet is spread."

Uchiha Nagi nodded. "I don't need to rest tonight. This is for you to sleep on."

Kimimaro was stunned. "Ah, for me? Then you…"

Uchiha Nagi said, "You saw the person I fought. Before we leave the Land of Water, we must remain vigilant. Don't worry about me; ninjas can go two or three days without sleep without any issues."

Of course, it wasn't that he wouldn't sleep at all. He could just create two shadow clones to keep watch while he slept. The fatigue from the night watch would still be transmitted to the main body when the clones were dispelled, but comparatively, the recovery from rest would always outweigh the fatigue. His body would, after all, get some rest and recover a good deal of energy.

Inside the cave, the campfire illuminated Kimimaro's face.

Kimimaro had only been lying on the bedsheet for ten minutes before he drifted off to sleep with a blissful smile. Children his age tired easily.

"It seems it wasn't too difficult," Uchiha Nagi murmured to himself, looking at Kimimaro.

Uchiha Nagi hadn't been very confident about spiriting away little Kimimaro. After all, he wasn't an inheritor of the Will of Fire—a [Brainwashing Expert].

Yet, it had gone surprisingly smoothly. Uchiha Nagi scratched his head. Could it be that orphans are more trusting of strangers?

Uchiha Nagi wasn't the only one who spent a sleepless night. Orochimaru did as well. Nagi was worried about Kirigakure's Anbu and a potential sneak attack from Orochimaru, while Orochimaru was utterly astonished by the small smear of demon blood he had obtained.

He discovered that it was an exceedingly peculiar type of cell. If the First Hokage's cells were akin to plant cells, with a very strong rejection by the human body, even more aggressive than cancer…

Then these cells were like mutated human cancer cells. It was well known that human cells have a limited number of divisions, roughly around fifty times in a lifetime (Hayflick limit). As people aged, cell division slowed, vitality decreased, until the cells reached the end of their life, leading to various bodily functions failing in old age.

But mutated human cells, cancer cells, had no such restrictions; they could divide infinitely. Many people theorized that the secret to human longevity might lie hidden within cancer cells… because if the human body was no longer troubled by the limited number of cell divisions, it could achieve immortality.

From the bit of blood obtained from Uchiha Nagi, Orochimaru discovered it actually possessed the same characteristic as cancer cells: the potential for infinite division. However, some subsequent tests made Orochimaru frown. These cells were most interested in human hemoglobin as a nutrient.

In other words, their food was likely human blood…

When it absorbed the blood of other animals, like snake blood or bird blood, the efficiency of its division and reproduction was very low.

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