Black Zetsu pondered, then suddenly felt that this wasn't impossible; in some ways, the progress might even be faster than it was now. Although Black Zetsu wasn't afraid of waiting, if there was a way to speed things up, it would definitely go for it.
"What you said might not be a bad method, but the reincarnated individual's strength must reach a certain level before their power can awaken," Black Zetsu said.
"That Uchiha Ken has already awakened the Mangekyo Sharingan, and several years have passed. Is that not enough for Indra's chakra to awaken?" Uchiha Koya asked.
"This…" Black Zetsu mused. For Indra's chakra to begin awakening, the reincarnated individual's Mangekyo Sharingan must first be developed and used to a certain extent. However, this often leads to blindness. In the past Warring States period, reincarnated individuals were completely unable to obtain Asura's power.
But now, Uchiha Koya intends to merge Indra and Asura's powers himself, so there's no need to consider whether the reincarnated individual's eyes become blind, as long as Indra's power remains within the reincarnated individual.
"Although I haven't seen the reincarnated individual, theoretically, with several years of having the Mangekyo Sharingan, the power should have been developed to a relatively deep stage," Black Zetsu said.
It's not that continuous use of the Mangekyo Sharingan is necessary for deep development. Uchiha Itachi's Susanoo had been in its third stage for some time without losing his sight, while Uchiha Sasuke lost his sight immediately after entering the third stage. The frequency of use is what determines the Mangekyo Sharingan's loss of sight.
As long as Uchiha Ken hasn't wasted his time, these few years should have been enough to develop his Mangekyo Sharingan to the point where Indra's power can awaken.
As for Asura's reincarnated individual, Black Zetsu couldn't be sure. Uchiha Ken was clearly understood to be a master, but Asura's reincarnated individual was not as well understood.
Although there was a fated connection, the disparity in their abilities was not something destiny alone could decide. There were too many unexpected factors. In the Warring States period, there were examples of significant power gaps between reincarnated individuals, which would have made the revival of the Rinnegan impossible.
Black Zetsu had waited for a thousand years and encountered all sorts of phenomena. Otherwise, how could it have waited until Uchiha Madara's time to finally see hope?
However, the outcome of the Valley of the End battle left it utterly disappointed. Uchiha Madara died at the hands of Hashirama Senju, and everything had to start over.
"In that case, Indra's reincarnation shouldn't be a problem. It's just Asura's reincarnation that's unknown, right? From what I know, in everyday combat, the power gap between Asura's reincarnated individual and Uchiha Ken isn't too significant. I just don't know what the gap would be like after using the Mangekyo Sharingan, or if Asura's reincarnated individual has any trump cards," Uchiha Koya nodded.
"Then, my lord, you can find an opportunity to let me take a look. I can determine if both of their chakras have begun to awaken," Black Zetsu quickly said.
"Hmm, after those cultists are tracked down by the Konoha ninja village, you can also free yourself. Most of them can be abandoned, but those who have successfully mastered immortality can be brought back. You handle that well," Uchiha Koya instructed.
"Yes," Black Zetsu bowed slightly and said.
"By the way, how long does it take to cultivate the Rinnegan?" Uchiha Koya suddenly remembered something and asked Black Zetsu.
"It mainly depends on the degree of fusion of the reincarnated individuals' powers. As long as you can control the reincarnated individuals, I have ways to help you find methods to promote the fusion of their powers," Black Zetsu said.
"I understand that. By the way, the reincarnated individuals can't die, right? At least not before the powers merge," Uchiha Koya confirmed.
"Yes, if the reincarnated individuals die before the powers merge, then apart from the powers that began to merge while they were alive, all other powers will leave this world and await reincarnation," Black Zetsu replied.
Once a reincarnated individual dies, their chakra will also disappear. In the original story, Uchiha Madara transplanted cells containing Asura's power into himself while Hashirama was still alive. If he had waited until Hashirama's death to perform the transplant, the fusion of their powers would not have been possible.
Uchiha Madara's late awakening of the Rinnegan was, to some extent, perhaps due to Hashirama's early death, which made the fusion of Asura's power more troublesome.
"Heh, how troublesome. Luckily, my current strength has grown even greater, otherwise controlling those two wouldn't be an easy task," Uchiha Koya pouted.
"With your strength, defeating the current reincarnated individuals is no trouble," Black Zetsu said.
Uchiha Koya, after years of absorbing souls, was now even more formidable than in the past, and he also possessed the Mangekyo Sharingan, with a very troublesome and difficult-to-deal-with ability.
Even if Uchiha Koya couldn't defeat his opponent in one go, he could do it multiple times. His Mangekyo Sharingan ability was precisely like that; Fūma Asuhina suffered a loss because of it back then.
Asuhina's guess at the time was correct; Uchiha Koya wasn't using shadow clones to fight, but was truly present in person. He was able to escape using his Mangekyo Sharingan's ability.
Black Zetsu was Uchiha Koya's "pawn," and Uchiha Koya had no intention of hiding it, revealing some of his Mangekyo Sharingan abilities.
Uchiha Koya's Mangekyo Sharingan, to some extent, was similar to Uchiha Kagami's. His Mangekyo Sharingan also had a space for storing souls. Any soul of a person Uchiha Koya killed with his own hands would fall into his Mangekyo Sharingan.
Black Zetsu strongly suspected that this was due to the special ability of the soul within Uchiha Koya, influencing the Mangekyo Sharingan and thus giving birth to such power.
Just as Uchiha Koya himself could absorb the grudges of the dead to enhance his power, his Mangekyo Sharingan could absorb souls and, at the same time, extract combat experience from within those souls, thereby improving his own skills. Although he couldn't learn talents he didn't possess, even by absorbing experience, he could strengthen any talents he already had.
Besides absorbing souls to enhance his chakra, Uchiha Koya spent most of his time absorbing experience, and this was just the tip of the iceberg of his Mangekyo Sharingan's abilities.
Uchiha Koya could also use his Mangekyo Sharingan to release these residual souls to launch powerful mental attacks, which was a relatively conventional Mangekyo Sharingan genjutsu ability. Additionally, it could serve as a medium for a substitution jutsu, effectively allowing him to "die in place" once, a high-level substitution jutsu akin to Orochimaru's style.
The reason Uchiha Koya was able to escape that explosion was by using a residual soul as a substitute for his own death. Although this substitution dōjutsu had a distance limit, similar to ordinary substitution jutsu, and even shorter, as long as it was within range, its effect was no less than the instantaneous teleportation of the Flying Thunder God.
However, this required a complete soul, and it had to be a soul of someone Uchiha Koya killed himself, which theoretically would limit its application. But Uchiha Koya, through his special methods, ensured that the souls of people killed by those who consumed his secret medicine and had their bodies modified could all be stored in his Mangekyo Sharingan, becoming puppets for substitution.
Black Zetsu later learned that Uchiha Koya's purpose in supporting the Jashinists also included this. Even if a portion of Uchiha Koya's current power was used to enhance his own chakra, he should have accumulated a considerable number of substitute puppets. Even if he accidentally encountered an opponent he couldn't defeat, he would have a way to escape.
"Haha, what you say is true." Uchiha Koya was very confident in his Mangekyo Sharingan's abilities. At the same level, he only needed to sacrifice one or two substitute puppets to turn the tide, just as he did when he faced Fūma Asuhina, severely injuring her.
Of course, if he faced someone much stronger than himself, it would be more troublesome. While the substitute puppet was convenient, it was ultimately just a high-level substitution jutsu and had a distance limit. If the opponent launched a large-scale, long-lasting AOE attack, Uchiha Koya would be unable to escape and would be blown to smithereens.
This might be a flaw of this substitution dōjutsu; it seemed as convenient as space-time ninjutsu, but in reality, there was still a gap.
For example, Konan's six hundred billion exploding tags. Even if they only exploded for five minutes, Uchiha Obito's Kamui could turn the tide, but if Uchiha Koya didn't have enough substitute puppets to escape the range, he would be blown to death inside.
Of course, Uchiha Koya didn't know that such an ultimate AOE move would exist in the original timeline, but he knew that Fūma Masahiko could definitely use large-scale storms, powerful forces akin to natural tornadoes and typhoons.
These were intelligence Black Zetsu had meticulously gathered, deduced from the combat data available on Fūma Masahiko. Honestly, it had never understood why this ordinary descendant could possess the power to practice Sage Mode, and even advance to such a high realm.
Black Zetsu couldn't find an answer no matter how much it thought, only able to conclude that this individual was one of the rare geniuses who occasionally appeared in each era. But no matter how formidable Fūma Masahiko was, he couldn't possibly be stronger than its mother.
Kaguya Otsutsuki's power was unrivaled; nothing could defeat her except for the Six Paths – Chibaku Tensei created by the Yin and Yang Release.
In the original work, although Kaguya Otsutsuki was constantly criticized for her lack of combat skills, with her power, even without much skill, she consistently overwhelmed Naruto and Sasuke. In a direct fight, Naruto and Sasuke never lasted more than three rounds, only able to stall by using jutsus Kaguya Otsutsuki had never seen before.
Although reviving Kaguya Otsutsuki still required collecting the Tailed Beasts, as long as Uchiha Koya obtained the Rinnegan, with its immense power, even if he wasn't as strong as Fūma Masahiko now, he wouldn't be far behind in the future.
"Alright, that's all for now. I need to go back. That Daimyo fellow always wants to discuss how to deal with the Konoha ninja village with me. I'm getting more and more annoyed with him," Uchiha Koya said.
"If you are truly annoyed with him, you could find a time to control him with genjutsu. That would save you some trouble," Black Zetsu asked.
"Now is not the time. If I truly get fed up, I'll definitely do that, but not now. Konoha has someone with a Byakugan, and if he sees that the Daimyo is controlled by genjutsu, I'll be in some trouble," Uchiha Koya said.
Black Zetsu nodded slightly. If the lord was controlled by genjutsu, it would indeed be a handle handed to the enemy. It wasn't that it didn't understand, but it couldn't show too much of itself in front of Uchiha Koya, as that might cause Uchiha Koya to have negative thoughts about it. Black Zetsu understood the mentality of such self-proclaimed lords very well.
"I understand. I'll head back then. Do I need to react to any potential actions from the Konoha ninja village?" Black Zetsu asked.
"No need. Abandon everyone except those with true ability. It will allow the Konoha ninja village to believe they've gained an advantage, which will buy us time," Uchiha Koya waved his hand.
"I understand. Then, until next time, my lord." Black Zetsu's figure slowly sank into the ground, then disappeared, its presence no longer detectable.
"Indeed, a formidable stealth technique. I wonder if there's a way to break it in the future." Uchiha Koya silently watched the spot where Black Zetsu disappeared, then turned and left.
No one knew about this night's meeting. Uchiha Koya was now a favored minister of the Daimyo's court, holding a very high position and power. No one could discover his brief departure. And this time, when he went to meet the Daimyo with the other Guardian Ninja, a faint hint of desire was revealed in his eyes as he looked at Uchiha Ken and Fujimura Yuuki.
Although he wore a mask and no one saw Uchiha Koya's eyes, Uchiha Ken and Fujimura Yuuki's keen senses detected an unpleasant gaze. They secretly observed, confirming that the person might be Uchiha Koya.
Everyone knew that "Tobi" harbored ill intentions towards Konoha Village, so neither of them was too surprised. They simply thought that their past attempts to recruit Tobi had gone unanswered, leaving him somewhat disgruntled, and that he might treat their side harshly in the future, thus raising their guard.
Uchiha Koya anticipated that when the time came for confrontation, he could gather the chakra within the two reincarnated individuals into himself, once again summoning the divine power of the Six Paths Sage into this world.
At that time, he would be the second Six Paths Sage. Just as the Six Paths Sage influenced this world, he too would reshape this world, guiding it towards his desired direction. Anyone who dared to stand in his way would be mercilessly eliminated.