At age eleven, after five months of extraordinary service as a chūnin, Fugaku submits Itachi's name for consideration in the Anbu. The Third Hokage discusses this with Danzō, expecting him to oppose it due to his long-held distrust of the Uchiha. To the Third's surprise, Danzō is in favor of the idea. The Third has no objections other than Itachi's young age, so suggests that Itachi be given an Anbu-caliber mission to make sure he is ready. Itachi is mandated to take a week off from missions and training - all of which he ends up spending with Sasuke except for a lunch outing with Izumi - before being summoned to a meeting with Danzō. Danzō explains that before he can become an Anbu, Itachi must prove himself by assassinating Mukai Kohinata, a Konoha-nin who has been selling secrets to Kirigakure. Itachi, having long since decided that being an Anbu is vital to his dream of ending conflict and establishing peace, accepts the assignment.
Danzō permits Itachi to have the help of one other individual of his choosing in order to deal with Mukai. Itachi selects Shisui. Shisui already has some familiarity with Mukai and his skills: as a distant descendant of the Hyūga clan, Mukai excels in the Gentle Fist style of combat. Since it would be a good idea to have Itachi witness Mukai's abilities firsthand, Danzō arranges for a member of Mukai's usual team to be injured and has Itachi assigned as their replacement. Itachi accompanies Mukai's team on a mission to observe negotiations for a secret alliance between Kiri and Sunagakure. Their presence is discovered and they are attacked by twenty Suna-nin. Although Itachi intends to fight alongside Mukai's team in order to secure their escape, Mukai fights the twenty alone, defeating them all without difficulty.
