In an underground laboratory beneath Konoha...
Aoba stood before a cultivation pod. Inside was a young boy, Toneri, currently undergoing physical reconstruction.
Toneri's transformation was the most complex part of the entire Ōtsutsuki Enhancement Project, mainly because he wasn't originally from Konoha.
Although Aoba had him under control with Kotoamatsukami, once Toneri's Ōtsutsuki genes were fully completed, Aoba couldn't guarantee that he wouldn't break free of the genjutsu.
After all, Kotoamatsukami was hailed in the original story as the strongest genjutsu, but it never actually got a chance to show its full power.
Its original user, Shisui, died early. The first person to use it, Danzō Shimura, wasn't even an Uchiha, and he was so stingy with chakra he barely used it at all.
He managed to control a samurai named Mifune, but was still quickly seen through.
The other person who used it was Uchiha Itachi, and even then, he didn't cast it himself, it was implanted into a crow and released posthumously.
There was a clear trend with Sharingan abilities: the original owner, other Uchiha, outsiders, and even summoning creatures, all had completely different levels of effectiveness.
So in the original storyline, Kotoamatsukami never showed its true potential.
In Aoba's time, after acquiring the eye, he used it at full power and managed to completely control Toneri. But since he wasn't an Uchiha himself, he still wasn't sure if he was using the eye at its true limit.
Once Toneri's genes were fully restored and he became a true member of the Ōtsutsuki clan, Aoba couldn't be sure he'd remain under control.
So he needed an extra layer, or several layers, of insurance.
After separating from chakra, Aoba could no longer use the Sharingan, so the Kotoamatsukami eye from Shisui was eventually passed on to Itachi Uchiha, who now operated under the codename Crow.
After all, in all of Konoha, no one else was more suitable for that eye.
Six Paths–level Sasuke upgraded the Kotoamatsukami Mangekyō into a Rinnegan, and handed it over to Itachi, who, almost overnight, became a near Six Paths–level force.
However, Itachi's original body had long since been ruined. His current body was a clone fused with Hashirama cells. And since the eye wasn't originally his, he needed time to adapt to it.
That's why he hadn't appeared during the attack by Hashirama and Obito.
Now, he had basically mastered the Rinnegan. Aoba brought him into the lab to apply an additional layer of insurance onto Toneri.
At Mangekyō-level, Kotoamatsukami might be breakable, but at Rinnegan-level, that was another matter entirely.
And it wasn't just genjutsu, during Toneri's physical enhancement, the lab had implemented countless controls at the bodily, neurological, and even soul level to ensure this top-tier combatant would be 100% loyal to Konoha.
The soul-level modifications were overseen by none other than Orochimaru.
After arriving in Konoha, Orochimaru even began to regret it, regret not defecting sooner.
Because only once he arrived did he realize just how far Konoha had advanced in its understanding of chakra, genetics, and the human body.
Orochimaru had once relied on his Living Corpse Reincarnation technique to achieve pseudo-immortality, transferring his soul from body to body.
But Konoha had already achieved brain transplantation, a purely medical method of achieving a different kind of immortality.
Orochimaru had considered this path before, but lacked the high-level medical ninjutsu of someone like Tsunade, and more importantly:
Research of this caliber required massive resources, personnel, and deep scientific knowledge.
Orochimaru's personal reserves were top-tier for a lone rogue shinobi, but Konoha's research division had hundreds of experts. And with Tsunade leading them, they completely overwhelmed Orochimaru in every aspect.... Staff, funding, and data.
Plus, he had been a fugitive, constantly forced to move and go into hiding. In those conditions, real scientific breakthroughs were almost impossible.
After coming to Konoha, Aoba showed no hesitation. He opened up nearly all research data and gave Orochimaru full access.
In return, Orochimaru offered all of his research and cross-referenced it with Konoha's archives, becoming a key driver in the village's soul-related research.
Many of the soul-level safeguards placed on Toneri were developed by Orochimaru himself.
At this moment, Toneri's transformation was nearing its end. His enhanced Ōtsutsuki body had already triggered an early awakening.
And just as he began to wake...
A pair of eerie Rinnegan eyes appeared before him.
If you would like to read more...
The novel has be completed (Chp. 362) on the patreon -> SaintXI