Among all the countless Naruto characters, there is one who we have seen rarely and, for this reason, we have never paid so much attention to: I’m talking about the Spiral Zetsu.
We have seen him only in some Obito’s flashbacks and then he disappeared, but we know that Kishimoto never creates a character randomly, so it can’t be considered as useless. The point is: what happened to him? There must be a reason if Kishimoto created the Spiral Zetsu, so let’s try to understand it!
First of all, we all know that Madara created the Zetsus during Obito’s rehabilitation due to his misadventure and before Rin’s death; in addition, also the Spiral Zetsu has been created over that period specifically for Obito’s body, since he had a one-eyed face and his body could be used as a vessel for someone whose body had been crushed like Obito’s one.
Secondly, some traits of Spiral Zetsu manifested in some ways also in the guy called “Tobi”; in fact, Tobi’s mask seemed to be very similar to Spiral Zetsu’s face. From our experience we can find out that in Kishimoto’s work there have never been what we could call “coincidences”, so that their faces must have a connection if they look like so similar, don’t they?
Thinking about all these facts, now I’m going to introduce you my theory: in my opinion, what happened is that the Spiral Zetsu has been integrated with Obito’s body. Why?
Well, to begin with, when we saw Obito naked during the 4th Shinobi War, we saw that he possessed a part of his body completely made of Hashirama’s cells, and we know that Madara created the Zetsus thanks to those particular cells.
Then I’m also convinced that Madara was able to control the Spiral Zetsu and make him follow his will, so that when Obito’s body absorbed Spiral Zetsu, Madara became able to control also Obito’s will, in order to make him lead the Akatsuki and avoid some changes in his plans. In this way, the union between Obito’s body and Madara’s will brought to the accomplishment of their aim.