Board Thread:Naruto Discussions/@comment-26320638-20150422140407/@comment-3279282-20150422143753

BoltUzumakiXD wrote: Its just that it was also stated in sakura hiden that it was just a dream and about kabuto he said the studies so.....

I haven't read Sakura Hiden, but in the manga, Kabuto uses Hashirama's cells to heal Sasuke. Hence his Rinnegan.