Kage

A is the leader of one of the five most powerful hidden villages and are generally acknowledged as the most powerful ninja in their respective villages. They are collectively known as the.

Kages Hokage

Kazekage

Mizukage

Raikage

Tsuchikage

Overview
The term "Kage" is not used to just refer to any leader of any village. Only the leaders of hidden villages of the Five Great Shinobi Countries are referred to as such. The Kage oversee the activities of their villages, from sending ninja teams out on their missions to making the hard decisions regarding the safety of their people. The first Kage was the Hashirama Senju of Konohagakure. Following the Hokage title, emerged the of Sunagakure, the  of Kirigakure,  of Kumogakure, and  of Iwagakure.

Once a ninja is made Kage, normally by a predecessor, the title remains with that person for the rest of his or her life. While the previous Kage may retire, he may resume his role as leader if his successor dies as was the case with the Third Hokage Hiruzen Sarutobi. In the event that a Kage dies without naming a successor, an ideal heir could find a more suitable successor as is the case with the Fifth Hokage Tsunade. As seen with Danzō Shimura, a Daimyō has the authority to name a candidate Kage to serve as acting leader. Since the making of jinchūriki began, it became traditional for the host to be a relative of the current Kage, not only so that the host has deep loyalty bonds with the village, but also to serve as a display of the Kage's might. For example, both Killer B and three of his predecessors are related to the Third and Fourth Raikage, and Gaara is the son of the Fourth Kazekage. A much earlier example of this would be Mito Uzumaki who, after her husband, Hashirama Senju, gained control of the Nine-Tails, made herself its jinchūriki by sealing it inside her.

Though the Kage normally act on their villages' agenda, the actions of Akatsuki abducting jinchūriki, with Gaara surviving his near-death ordeal and Killer B and Naruto Uzumaki the only active jinchūriki not captured, the Kage gather at a summit at the Land of Iron to discuss how to deal with the organisation. However, with Danzō as the Sixth Hokage candidate to represent Konoha in place of a comatose Tsunade, the Kage argue amongst themselves over what course to take until their moderator Mifune proposed an alliance to confront Akatsuki. Though Danzō is nominated to lead, he's exposed as having manipulated in doing so. The appearance of White Zetsu and Taka at the summit allows him to escape, and A, previously considered unfit due to his emotions, is named leader of the newly formed Allied Shinobi Forces upon learning the goals of the masked ninja identifying himself as Madara Uchiha.

Trivia

 * In the anime, Hoshigakure has unofficially dubbed each of its leaders the, signifying their ambition for Hoshigakure to be recognised as an equal to the hidden villages of the Five Great Shinobi Nations.