Saga

サガ

Saga is the 'main antagonist' of the fifth movie. He is a childhood friend of Zoro's (they both trained at the same dojo) and a friend of Maya's, as well as her possible love interest. The real Saga is a friendly, honorable, and ambitious young man.
He fell into depression after losing the use of his right arm, but Maya brought him out of it when he drifted to her island. He was accepted into her village and later fought alongside them when pirates attacked.
During the battle, he and Maya entered the shrine housing the Seven Stars Sword. He fell under the sword's evil influence when he used it out of desperation to save her from the pirates. The sword possessed Saga, driving him to try to reach full power and bring darkness to the world. Saga took over and possessed an entire Marine dojo to aid in this quest.