Kakuzu is mainly introduced as one of the Akatsuki members. He is partnered with Hidan and wears the ring, Hokuto.
A member of Takigakure, the Village Hidden in a Waterfall, and the partner of Hidan, Kakuzu has a lust for money and uses his involvement with Akatsuki as a means of seeking out bounties. Kakuzu only relies on money, and as such hates being paired with anyone from Akatuski. He has even managed to kill all his previous partners, and as such was paired with Hidan because of his immortality. His body is made up of black threads that can be used to sew things, but are also able to pierce flesh, which allows him to remove body organs of his opponents to be used in his forbidden technique called Jiongu. Using these hearts, Kakuzu is able to extend his life span. He keeps four spare hearts in animal masks on his back. The masks can also be used as weapons during battle, where they can detach and shoot elemental blasts at the opponents.
Kakuzu spare hearts are destroyed by a group of Konohagakure ninja, and after Naruto leaves his final heart hinging on its last string, Kakashi comes in and finishes him off.