Board Thread:Theories and Speculation/@comment-27717552-20160513151229/@comment-9782468-20160611035814

Both rely on the highest calibre of one of the two sides of Ninjutsu. The Rasengan requires the highest form of Shape Transformation. Kakashi couldn't combine his Nature to it, so basically what he did was create a counterpart. Chidori and Raikiri are the highest forms of Nature Transformation. And he made it as a weapon to thrust into an opponent. just like the Rasengan. So yeah, they're similar.