Uchiha Izuna: It was left behind by my elder brother.
Uchiha Izuna: This part of the content should be about the Eternal Mangekyo Sharingan.
Senju Tobirama: "Has the Eternal Mangekyo ever appeared in your clan's history?"
Uchiha Izuna: No.
Uchiha Izuna: The conditions for awakening it are both harsh and not harsh at the same time.
Uchiha Izuna: To evolve the Mangekyo Sharingan into the Eternal Mangekyo Sharingan, a transplant is required... perhaps with an additional condition: a close relative?
Uchiha Izuna: Before I died, I let my elder brother transplant my eyes, and he agreed... as a result, the Mangekyo Sharingan evolved!
Uchiha Izuna: Because of years of fighting, overusing the Mangekyo Sharingan was inevitable. My brother's eyesight was even worse than mine; relatively speaking, my eyes would have lasted a bit longer than his.
P.S.: A small change. In fact, a situation more consistent with the timeline is: after Uchiha Izuna's death, another great war occurred, they were defeated, Konoha was established, and Uchiha Madara deciphered the stone tablet and learned of the existence of the Eternal Mangekyo Sharingan (Black Zetsu), or perhaps he deciphered the stone tablet before the war to find a way to save his younger brother.
Ino Yamanaka: "Handsome Godfather..."
Uchiha Izuna: It's fine. At that time, after hearing my elder brother say this personally, my last breath faded away, and I was at peace.
In the Pure Land World, Uchiha Madara remained silent.
At this moment, Senju Tobirama suddenly said:
"No, besides being close relatives and both having to be possessors of the Mangekyo Sharingan, there might be one more condition!"
Uchiha Izuna immediately understood.
Uchiha Izuna: You mean... as my elder brother just mentioned, the reincarnation of Indra, the eldest son of the Six Paths Sage?!"
Senju Tobirama: "That's it!"
Senju Tobirama: "I see. My elder brother must be the reincarnation of the Six Paths Sage's later child, right?"
Since the eldest son was mentioned, there must have been more children after him.
And, in all probability, he is the ancestor of those with the sage body.
Senju Tobirama: "Furthermore, my elder brother and Naruto are the same reincarnation!"
Senju Tobirama: "No wonder I felt it was strange before... If that's really the case, then it seems quite normal for the Naruto of our world to be like this."
Senju Tobirama: "Also, Black-framed Naruto-kun said he dislikes Sasuke... Sasuke might also have whispers... it all makes sense now!"
["Eternal... Mangekyo Sharingan."]
[Naruto murmured.]
["If it's close relatives... no, the Uchiha Clan rarely marries outside the clan anyway; maybe you and Sasuke can try it in the future."]
["Besides, there's also that Uchiha Itachi."]
["Three pairs of eyes... a match will eventually be found."]
["But now there's another problem."]
["The Descendants of Indra, the eldest son of the Six Paths Sage—the Uchiha Clan."]
[As Naruto was thinking, Izumi suddenly continued speaking.]
["My eldest son... fought a great battle with my second son, Ashura... Indra was defeated... After the two died, the battle did not end... but continued through constant reincarnations... continuing their fated battle..."]
[Boom—]
[Naruto's entire body shuddered.]
[This is it!!!]
[Wife Izumi's deciphering was even more stumbling, indicating that this part of the content was not yet fully revealed, but this general event immediately cleared up many of Naruto's doubts.]
[whispers!!!]
[The Uzumaki Clan and the Senju Clan are distant relatives, so it's very likely they both belong to the Descendants of Ashura, the second son of the Six Paths Sage.]
[sage body... Sage Eyes... interacting with each other, All Creation!]
[Uchiha Madara is the reincarnation of Indra; perhaps because of this, he awakened the Eternal Mangekyo Sharingan... he planned a great war and obtained the sage body... Senju Hashirama, the First Hokage... the reincarnation of Ashura!]
[The two reincarnations both carry Chakra... the fusion of the two Chakras is equivalent to perfectly inheriting the power of the Six Paths Sage... the Rinnegan!]
[Uchiha Madara possesses the Rinnegan!]
[A thin layer of cold sweat broke out on Naruto's forehead, and his back was also soaked with sweat.]
[In just a few breaths, he seemed to have deduced an incredible secret.]
['Looking at it this way... like Senju Hashirama, I am the reincarnation of Ashura... the whispers... the Chakra in my head... Ashura? A foolish, naive, do-gooder... Senju Hashirama's way of thinking... it all makes sense now!']
['Then, did the previous generation's Indra, Uchiha Madara, who obtained All Creation... continue to reincarnate?']
['If he did... then Uchiha Madara must be dead by now, and Uchiha Obito has become his successor... Sasuke is very likely the reincarnation of this generation... No wonder I felt like punching him; it turns out it's because of the fated battle...']
['But, a new problem arises.']
['Why did Uchiha Madara plan all this?']
['Different ideals? Or an inevitable battle?']
['Or... is something guiding Uchiha Madara to do all this?']
[Black Zetsu: "..."]
[This is getting boring if you're like this.]
[Seriously!]
[Black-Framed Naruto, you're really taking all the fun out of this!!]
['Logically, if Uchiha Madara... really wanted to experiment, he could have just gone to Senju Hashirama... Senju Hashirama even agreed to let his body be studied after his death... just like a respected Silent Mentor.']
['And then he planned the Uchiha Obito incident... what he wants to do is definitely something big, and it's something most people wouldn't approve of... even Senju Hashirama would stop him.']
['Senju Tobirama's targeting of the Uchiha... it's also possible that Uchiha Madara asked, Senju Hashirama agreed, but Senju Tobirama refused.']
[Naruto felt a bit confused, but countless flashes of inspiration kept crossing his mind.]
[It felt as if an invisible hand was preventing the truth from emerging.]
[Setting up layer upon layer of obstacles.]
["Let's put the matter of the Eternal Mangekyo aside for now."]
["Uchiha Madara and his younger brother Uchiha Izuna were the main forces of the Uchiha Clan."]
["They fought against the Senju Clan for many years."]
["There are no records of them going blind... as long as the Mangekyo Sharingan isn't constantly overused, it can be used for a long time."]
["Just like Uchiha Itachi and Uchiha Obito."]
[Naruto took a deep breath, suppressing his restless heart, but Sasuke's figure appeared in his mind at just the right time.]
['If it's Sasuke...']
[He shook his head.]
[Things will work out when the time comes. Even if Wife Izumi is unable to awaken the Eternal Mangekyo Sharingan in the future due to the lack of Indra's Chakra,]
[at that time, I can also convert a lot of highly resilient Chakra through the whispers... plus the Great Fox's golden Chakra, or in the worst case, I'll personally research Senju Hashirama's cells...]
[At this point, Izumi also began to decipher the fated battle between Indra and Ashura in detail.]
[Naruto suddenly had an idea.]
['Since Uchiha Madara could achieve All Creation, can I also achieve All Creation?']
['As long as Sasuke awakens the Mangekyo Sharingan and then obtains Uchiha Itachi's Mangekyo Sharingan, awakening the Eternal Mangekyo Sharingan is a certainty.']
['Then... should I transplant Sasuke's eyes?']
['Or, should I also transplant the cells (Tissue Culture) left behind by Uchiha Madara and Senju Hashirama?']
['All Creation... it probably refers to obtaining and inheriting the true, complete power of the Six Paths Sage, right?']
['Ōtsutsuki?']
[I've never heard of it... but...]
[Could it be related to this surname?]
[Just then, Izumi's deciphering voice suddenly hitched, and then she said:]
["Infinite Tsukuyomi..."]