Board Thread:Naruto Discussions/@comment-34569788-20180504183427/@comment-734582-20180506065751

Minimigitthe1st wrote: It is literally stated to be an evolution of sharingan. Which was debunked by the Manga quite hard, since it turned out that the Rinne Sharingan is the progenitor of both Sharingan and Rinnegan lines (and not the other way around).

Lorenzo.r.2nd wrote: @thekillman the last part is super, omega arguable though, since sasuke did use his ms abilities in his rinnegan state, while his rinne was active, and without having to switch back. And he has Tomoe in his rinnegan, which de-activate when his MS deactivates. Thereby proving the initial point, that they're separate dojutsu active at the same time. Madara and Hagoromo have no such tomoe, and Madara was never shown to use MS powers with Rinnegan.

JamesSenpai wrote: I think Kabuto pumping Sasuke with Hashirama's cells is the only thing that makes sense on how he awakened Rinnegan. The Databook states that he got it from Hagoromo. Not from his chakra or anything, from Hagoromo. Same for Naruto's SPSM. Yet when Obito had his chakra, he didn't get his own Rinnegan, nor did Kakashi when he got chakra from Obito. So it can't be chakra transfers.

This leaves the option i pointed out earlier:

Naruto has the spirit half of the juubi (in the form of 9 tailed beasts). Hagoromo manipulated that power to bring forth SPSM. Sasuke had Zetsu cells, Hagoromo manipulated that to give him Rinnegan without losing MS. He did something similar by splitting the Juubi, so it's well within his power.