Kisame: Beast Without Tail

Kisame Hoshigaki  known as the Monster of the Hidden Mist, was an S-rank missing-nin from Kirigakure. He was among the Seven Ninja Swordsmen of the Mist and was partnered with Itachi Uchiha when Itachi joined Akatsuki.

Originally, Kisame was a guard of the Cypher Division under orders from his seniors, Fuguki Suikazan of Seven Ninja Swordsmen of the Mist. When the group was cornered by Konoha-nin under Ibiki during a mission, Kisame chose to kill his own comrades to keep their intel from being leaked out through, as instructed by Fuguki.
Kisame then kills Fuguki and takes Samehada.

Finally, learning that Fuguki was leaking information to other ninjas, Kisame killed him and took Samehada for himself while replacing his superior as one of the Seven Swordsmen. After that Kisame was given the title of "Monster of the Hidden Mist", and formed a relation with Suigetsu Hozuki and Mangetsu Hozuki.

While approached by the Fourth Mizukage Yagura to be commended him for his loyalty to Kirigakure, the ordeal from killing his fellow Kiri ninja to reach his status as a Mist Swordsman caused Kisame to become disillusioned and see himself as living a lie. It was soon after that Kisame met a unknown ninja who was manipulating Yagura from the shadows and called himself Madara Uchiha. Learning of the 'Eye of the Moon Plan', Kisame was initially sceptical of the mysterious ninja, but later he joined Akatsuki and became the most loyal members of the Akatsuki

Kisame eventually became a missing-nin when the Land of Water sought him for plotting to overthrow its government and being involved in numerous assassinations that include another country's Elite. As a full-time member of Akatsuki, Kisame was partnered with Itachi Uchiha. Though they initially greeted each other with hostility, they became good partners Afterwards.