Board Thread:Naruto Discussions/@comment-9567825-20140910102105/@comment-24593592-20140913114551

Jashin Uchiha wrote: Man of Sin wrote: Elveonora wrote: People's logic: 5 Kage wanted to kill Sasuke - a person that isn't even an adult yet, they are good guys of course. Sasuke wants to kill the Kage: HE IS EVIL!!!!

Sasuke is considered an adult in the Narutoverse. 15 is old enough to be a Kage.
 * First of all he's 17 (Naruto's 17th birthday just passed and he is a week older)
 * Second of all Garra (the current Kazekage) is the same age as Sasuke (and Naruto)

Gaara was 15 when he became a Kage.