Board Thread:Naruto Discussions/@comment-26006790-20141130031518/@comment-5936871-20141130191559

Hagoromo told Yang Kurama that he had to go back inside of Naruto and stay with him because he wanted him to protect the vessel of all the Tailed Beasts, which is Naruto, and Kurama reluctantly complied.

Then at the end of chapter 700, we see one sleeping Kurama in what appears to be Naruto's subconscious, who has the regular colored fur that Yang Kurama and the original Kurama has as well. So Yang Kurama must have been resealed into Naruto, merged with Yin Kurama, and returned back to his complete Yin-Yang self.