The Hoshikage (星影, Literally meaning: Star Shadow) is the leader of Hoshigakure. The title of Hoshikage is merely a formality within Hoshigakure as it is not recognised as a true Kage by the other hidden villages. By calling their leader a Kage, Hoshi hoped to one day be recognised by the great villages.
The Third Hoshikage was killed by Akahoshi, and he became the Fourth Hoshikage for a short time. After the people of Hoshigakure discovered he killed the Third Hoshikage, he was defeated by Naruto Uzumaki and given to the proper authorities. His fate and the next Hoshikage are unknown.
List of Hoshikage
Main article: Akahoshi
There was never an official Fourth Hoshikage (四代目星影, Yondaime Hoshikage, Literally meaning: Fourth Star Shadow). Akahoshi claimed to be the Fourth, but was never given the title. Sumaru wanted that title as much as Naruto wants to become Hokage.