Obito and Shisui, The Nameless Shinobi's
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As you can see, Obito is considered a nameless shinboi who sacrificed himself for others.
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^ In this link, it elaborates on who they were talking about specifically. Which was Obito.
This idea of a true ''Shinboi'' is brought back up again, this time by Itachi.
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This is obviously Kishimoto foreshadowing here.
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Obito elaborates even more of what a true hero/shinboi is. He later goes on to emulate his words of that.
Tobi used to command Akatsuki what to do in the shadows and still kinda is in the shadow since only now he doesn't want to reveal himself. He says he's no one because he considers himself a nameless shinboi, this fits the description of Obito and Shisui. This is what the manga has been indicating so far.
It appears he has some of Uchiha Madara's power:
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Here he's clearly saying Uchiha Madara powers are his power. This is implying that he's placed his powers inside him of which is not really surprising considering the fact he's done the same with Hashirama's powers. I know your saying why would Obito take Madara's powers when he himself is an uchiha. Well, Madara was considered to be the strongest person with very strong chakra's to ever be produced in the Uchiha clan and the most gifted shinobi in history. With Hashirama being also the strongest one of his clan and the only one being able to use Mokuton. injecting both of the strongest of the SO6P son's descendants that were alive powers in him in order to reach the magnitude of the almighty power of the Rikoudo as much as possible. Any less would take him a few steps back from reaching that power. They'll be able to use the sage's techniques, but they wouldnt be as strong as him. Nagato couldn't make Chibaku Tensi as big as the Rikoudo sage. He had the will power and the physical energy to do it but he lacked the powerful chakra and spirtual energy to produce it just like the sage did. You see what im saying?
Madara and Hashirama are the ying and yang of the Sage of Six Paths. In other words, they are the rebirth of the Rikoudo's sons.
Anyways, moving on. Let me show you guys something:
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Who is Madara referring to as ''him''. How do we know if he isn't referring to Zetsu? It was said Zetsu was created shortly Madara obtained Hashirama's DNA. Ever since Madara survived the battle with Hashirama and created Zetsu, Zetsu has been an accomplice to him and the modern supposedly Madara. It would make a lot of since if he was referring to Zetsu, the main and first creation of Zetsu. Zetsu is really the one calling the shots just like when we thought Pain was running it when it was really Tobi. Zetsu is a fragment of Uchiha Madara's powers, the black one. On his deathbed or wherever he died, he hoped that his creation would live on and continue his ambition of taking over the world with the moon's eye plan. Madara probably lived up to as long as when he met Nagato. Zetsu was a boost to his lifespan. Basically, the first Hokage's cells had something to do with the increase of his lifespan. Madara later died for an unknown reason and awakened the rinnegan shortly before he died. It seems as if Madara knew how to awaken the rinnegan and the repercussions of doing so. So his plan was to give the rinnegan to Nagato so that later on when he grows up and knows how to use it, he'll revive Madara. Zetsu is the one who really gave Nagato the rinnegan.
Sometime after that, he runs into Shisui or Obito. It is possible that he attached half of himself into Obito since half of his body was crashed, so why not? Obito is a perfect vessel, he's missing half of himself. This could explain Tobi' split personality.
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''Beyond what you were in your prime''. He says it as if Madara lived past his prime. Kabuto somehow did a benjamin button on Madara and put an increase to his power. I think this is what Kabuto meant when he said his impure world resurrection surpasses that of the 2nd hokage and Orochimaru. So this is an indication that Madara lived past his prime into an old man to meet negato, who for some reason madara thought was the right vessel of wielding his rinnegan. Maybe Nagato's father was an Uchiha?
Now let's talk about Shisui now.
It is said Shisui had the power to enter the opponents mind and manipulate them by giving them false experiences, making it seem as if they were doing things on their own free will; the victim wouldn't even notice they were being manipulated.
Ao, a shinobi who fought Uchiha Shisui says Shisui was the one that manipulated the 4th Mizukage:
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This Kishimoto foreshadowing also.
''Self-Sacrifice.. A nameless Shinobi who protects peace from within its shadow... that is a true shinobi'. With that said, Shisui supposedly disappears, at least his ''body''. It is very possible that Shisui faked his death by using a kage bunshin the same way Killer B faked his death in order to flee in to the shadows where anyone that knows him doesnt know. It was said Shisui was spying on Itachi because he was acting strange half a month of being in ANBU. Was Shisui manipulating him the cause of his weirdness or was it just because of what the Kohoha advisories were telling him?
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As you can see his Mangekyou Sharingan is activated before he disappears, but why?
I think this is there by indicating he casted a jutsu on Itachi.
Look, Tobi definitely has some type of connection to Shisui most definitely. The fact that Zetsu popped out of underground before Ao could elaborate on Shisui is indicating Zetsu was possibly trying to cut him off of saying anything about him. Why? because he is most likely the guy behind the mask. The ''nameless shinobi'' is connected to both Obito and Shisui.
''nameless shinboi'' and ''no one'' definitely is the keyword on figuring out who exactly Tobi is.