"The Secret of the Impure World Reincarnation" (穢土転生の秘密, Edo Tensei no himitsu) is chapter 520 of the original Naruto manga.
Summary
Naruto continues to practice making the Tailed Beast Rasengan. Madara orders Kabuto to kill Anko, but he says he can get stronger by getting Orochimaru's chakra in her, so instead, he has Kabuto show him how Summoning: Impure World Resurrection works, by having him use Fū to resurrect Torune, whom he just killed. Kabuto does so. The Allied Forces learn of the Zetsu Army moving underground. The Surprise Attack Division continues their assault.
