Board Thread:Theories and Speculation/@comment-4688597-20150529040116/@comment-945885-20150530004513

The section from Shikamaru Hiden doesn't overtly state that Naruto's Six Paths Sage Mode comes from the nine biju, exactly, but it does sort of draw a line from Six Paths Sage Mode to the Six Paths Ten Tails Coffin Seal by saying that being Ten Tails' Jinchuriki gave Obito power rivalling the Sage of Six Paths, and that Naruto had also sort of become a Ten Tails' Jinchuriki by obtaining a portion of the chakra of all the biju, and that he still had a portion of their chakra, so he still has a portion of the Sage's power.

And, again, you can sort of draw the same conclusions from reading the databook, with regards to the Truthseeker Orbs manifesting upon awakening the power of the Sage of Six Paths, and that the Ten Tails Coffin Seal and Six Paths Sage Mode are two ways to do that. And of course they both have the Six Paths crest appear on their back, and that's what Madara looks at when he identifies that Naruto has gained the ability to use Six Paths Sage Arts.