"The Next Step" (次なる段階, Tsuginaru Suteppu) is episode 76 of the Naruto: Shippūden anime.
Kakashi reveals that the Rasengan is an incomplete technique as he is not able to combine his own elemental chakra affinity into it, just as its creator, the Fourth Hokage, couldn't do. He then presumes that Naruto might be the first one to be able to do so. Meanwhile, Asuma sends word to the other teams about the Akatsuki's location and proceeds on. Kakuzu then exchanges Chiriku's corpse. Naruto's training increases his stress to the point that the Nine-Tailed Fox tries to break free, but Yamato manages to suppress it entirely.