Sasuke Uchiha
When Itachi Uchiha is first mentioned by Sasuke Uchiha in the manga, Masashi Kishimoto had not planned out the character's backstory. The only idea he had was to attribute to Itachi some violent action that would have Sasuke wanting to kill him. However, when Itachi was introduced, Kishimoto had the idea to make Itachi Konoha's secret agent who killed his clan under their orders. Itachi was originally conceived as the leader of Konoha's Special Assassination and Tactical Squad called the "Anbu", dubbed the , which would have been a 70-man group divided into four teams, specializing in assassination and other illicit operations. However, this idea was scrapped in favor of the current Itachi working for the Akatsuki. From all the Akatsuki characters Kishimoto designed, Itachi is his favorite based on his backstory.