Board Thread:Naruto Discussions/@comment-34569788-20180504183427/@comment-734582-20180506135837

LegionZero wrote: Total speculation. There is nothing to suggest that Hagoromo did anything other than grant those abilities unto the 2 of them. It is questionable whether or not Tailed Beast chakra is necissary for 6 Paths Sage Mode. Naruto's SPSM is unlike normal six paths senjutsu, while Sasuke's Rinnegan is unlike other rinnegan. I think it's fairly obvious that Hagoromo is the reason why they are different. The fact that he could take something and change it as he saw fit as he did with the Juubi, proves that it's well within his power.

Sasuke got hashirama cells, but it can take decades to awaken Rinnegan. Sasuke got it instantly. Naruto had the Biju's chakra, yet did nothing and couldn't use it until Hagoromo came along. Clearly, hagoromo did something with the Biju. We don't know what, but it resulted in Naruto's SPSM.

From multiple angles, it all comes back to the fact that Hagoromo somehow intervened with their power, giving Sasuke his unusual eye and Naruto his unusual Sage Mode.

LegionZero wrote: It is also possible that the Rinnegan is within an Uchiha eye and is reactive to Hagoromo's chakra, only activating if it is empowered by 6 Paths Chakra. Obito had a Sharingan and got Hagoromo's chakra via the Rinnegan, yet it didn't give him a Rinnegan. When he obtained the Juubi's chakra it also didn't give him Rinnegan.

It's like all the flesh of ashura is a "blue color" and all the flesh of Indra is a "yellow color", and by getting some flesh of the other it gradually changes into Hagoromo's "green color". An Ashura's eyes would react and get Rinnegan just as an Indra would.

it is not normal for a Rinnegan user to also have Sharingan, because these powers do not normally coexist (See: Hagoromo and Madara, both natural Rinnegan users) whereas in Sasuke they were forced to coexist (thanks to hagoromo). the fact that the Tomoe disappear when his Sharingan powers fade, shows that it's not a singular dojutsu but rather two dojutsu coexisting.