Board Thread:Theories and Speculation/@comment-25319479-20180502154141/@comment-33486170-20180503150314

I would like to point out that he learned the Rasengan, indicating that he was taught it or he saw someone use it, since it is clear on who the users are indicates that he has met with them (i.e Naruto, Konohamaru, Jiraya, Minato, though Kakashi only used it infront of Naruto and Yamato).