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This picture that was posted on this same page lol. Itachi doesn't say anything about needing Senju DNA and we know he has all the knowledge because he knows of Izanami and even how to use Izanami, if he knows how to use Izanami he sure as hell knows how to use Izanagi and he clearly says "UCHIHA eyes have the power to blah blah in exchange for losing their own sight". THAT is the default Izanagi. Danzo was able to use it for 60 seconds because he had Senju DNA. All Senju DNA does it make it more powerful.
For example :
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Tobi even says that the people who couldn't control the Senju DNA had an INCOMPLETE Izanagi. I will say it again. Senju DNA is required to use the technique to the FULLEST. It is NOT required to simply use the technique.
One other thing, Izanami is a technique on par with Izanagi that according to Itachi form a pair. If Izanagi is a technique used originally by the So6p then Izanami must also be on the So6p level yet Itachi can use it and he has no Senju DNA at all.
I'll say it again. WHY would the Uchiha clan forbid a technique that required Sharingan AND Senju DNA to use? More importantly no one had both of those things... which means if Izanagi did indeed require both Sharingan and Senju DNA then how was it forbidden? The first person to have both Sharingan and Senju DNA was Madara and no one even knew he obtained Hashirama's DNA so that can't be used.
Do you understand that? A technique can't be forbidden if no one could USE it. If Izanagi required the user to have Sharingan and Senju DNA then tell me this, who was the one using it? Hmmm?