Board Thread:Naruto Discussions/@comment-3232093-20140617193601/@comment-28861328-20140618061550

Elveonora wrote: I believe that he had a Sharingan too, but no upgrade did happen. He simply had both since birth, two sides of the same coin. Not a coin that got polished later on.

Well, you can no longer use the argument that all chakra (and the eye) came from the Shinju. Seems Kaguya was the progenitor all along and the Ten-Tails was just a manifestation of her will.