Hiruko vs. Two Kunoichi!

is episode 20 of the Naruto: Shippūden anime.

Synopsis
Chiyo explains to Sakura that Sasori used to be one of the best puppeteers in Sunagakure, but he left the village after he started making puppets out of humans. Chiyo also reveals that Sasori's true body is hiding within his favorite puppet, Hiruko, and the only way to kill Sasori is to first destroy his puppet. Chiyo and Sakura are able to dodge Sasori's poison and with and Chiyo stopping Hiruko's tail with her katana,they successfully demolish the puppet using Sakura's strength. Sasori then emerges from the puppet's remains. Just outside, Deidara begins telling Naruto and Kakashi how much stronger Sasori is compared to himself.