It's hard to say how he stayed alive but inzanagi would have to be the case. Or quite possibly since he is the direct descendant of the sage, he could have some form of the "long life span" that was passed down to the uzamaki clan. I know they would be off opposite sides of the tree since that blood line would have came from the youngest son. But I have to believe that the 2 sons of the sage shared both senju and uchia blood since the sage had both, and over time the 2 clans emerged. To me there is no other member in the naruto universe that could be that manipulative, display that much wisdom, than the eldest son. I believe he was there when the 1st hokage and madara fought, and it was by his hand they were actually killed.
There is no way Tobi is the sage, the beast would have recognized the sage and the sage would not be "using" the beast the way Tobi is. The 9 tails dispises Tobi because he reminds him of madara. The beast loved the sage and would immediately recognize him. Additionally the nine tails reffered to naruto as the sage when he sealed him back when he was learning to control kurama.
He cant be obito because obito was no where near Kakashi's level when they fought in the kakashi arc. Kakashi was appointed to captain of the squad and minato went off alone. That being said how would he develop so quickly as to be able to control the 9 tails only a few years later, and spar with the 4th hokage and kill Anbu members silently, just from training on his own for a few years. Come one people obito is dead! An he was to weak to pull off something like this.
The only uchia the manga never tells us about is the oldest son of the sage. We know the oldest killed the youngest out of anger from he father not choosing him as the successor. Every other uchia is listed as dead when itachi slaughtered the clan with the help of Tobi. We know itachi was bad ass but someone with equal or greater power would have to help him pull that off.
Additionally Tobi says "I am no one" I think that's a hint because of the way he felt when his father did not chose him. He felt like a nobody and cast aside. Y his father. Lastly to support it, the sage made a promise to the beast that thus would be reunited one day, I believe he knew what was in his sons hearts and that this would all unfold in the future and he attached some of his chakra, or wisdom Into the beast so that it could be used one day. Since the sage is said to be the creator of all things, seeing the future isnt far fetched. We know the great toad sage can see the future, why not the SOP?
Again I think Tobi has too much first hand experience as to what happened with the SOP, and all the history between the senju and uchia not to be someone extremely powerful. And lastly we know he had the rinnegan and gave it to nagato. The only other person we know for sure who had the rinnegan besides the sage was uchia madara and the sages eldest son, who was "given the saves eyes"
Also on the first page of 564, naruto and Tobi meet "head to head" this is classic kishi imagery. Think about it what does naruto stand for, the senju / will of fire and everything "Good" and Tobi is the opposite the Uchia - revenge, hatred everything "evil". They meet head to head like a clashing of ideas. The same way naruto and Saske clashed fist to fist. Naruto was in his 9 tails mode which allows him to "sense evil" right. So he went straight towards Tobi full speed with a headbutt. We saw him head butt gara and it made gara bleed so we know it has some effectiveness, and with 9 tailed mode should be a little more powerful. Now why didnt it even scratch his mask? I think it's because they actually "repelled" one another. They are direct opposites, it is the sages will passed onto the youngest son, and Tobi being the eldest son could not just phase directly through this energy. Tobi has to be the oldest son of the sage.
Also when madara enters the battle he says "this is his doing" madara knows Tobi's identity. And kabuto confirms it and says "he is HIS assistant" kabuto knows tobi's true identity. And madara was kabuto's trump card. So again what other character could warrant kabuto to take precautions? I dont think it was izuna because we see madara's eyes and it is the EMS. The only way he could have the EMS is by taking his brothers eyes. So if his brother stayed alive when his eyes were removed he would be useless, without the sharingan
