Board Thread:Naruto: The Last Discussion/@comment-25824723-20141207101850/@comment-945885-20141215231100

I assumed he has Yin Kurama sealed inside of him and summoned Yang Kurama. The only time we've seen a Jinchuriki summon their Biju was in Road to Ninja, when Menma and Naruto both summoned Kurama and rode him. In either case, I wouldn't imagine that he could use Kurama Chakra Mode if Kurama was outside of him as a seperate entity.

So maybe he has both halves in him and summoned one to fight, or maybe he only has one half. I don't think it's been explained so far, unless the novelization clarifies it.