Itachi's Power!! (イタチの能力!!, Itachi no Chikara!!) is chapter 148 of the original Naruto manga.
Itachi tells Sasuke that he is still too weak. Jiraiya tries to capture him and Kisame but they flee, managing to escape from his Summoning: Toad Mouth Bind with Amaterasu. Jiraiya takes a sample of the flames for future study and Naruto checks on Sasuke. While they are preoccupied, Guy appears and attacks Jiraiya, having thought he was Itachi or Kisame. Naruto expresses an interest in going after the Akatsuki members, but Jiraiya tells him he would stand no chance against them. Because of the condition Sasuke and Kakashi have been left in after their encounters with Itachi, as well as Lee's predicament, Guy regrets that Tsunade is no longer in Konoha. Jiraiya tells him that they are in the middle of searching for Tsunade, the world's greatest medic.