B't X

Teppei Takamiya looks after a farm on Kamui Island, which is located north of Japan. His older brother Ktar Takamiya, one of the world's most brilliant physicists, leaves to study robotics in Germany. Five years later, the two brothers meet up again at a robotics conference in Mechatopia, China, where Ktar will be making a major AI announcement. When Ktar is taken to The Area by the evil Machine Empire, the convention is thrown off track. When Teppei makes it to the Machine Empire on his brother's behalf, he is ambushed by Metalface, one of the Empire's troops. Teppei is tossed in the junkyard of the Empire, bleeding, having failed to win. The resentful B't awakens as his blood reaches the wrecked body of X, who was formerly regarded as one of the Empire's strongest B't. In the face of unsolved issues and oncoming devastation, X unwillingly saves Teppei, and the two leave the Area with Empire soldiers after them. The ultimate B't, known as Raphael, has started an ominous and uncontrollable evolution, and Ktar learns that he has been called by Major Aramis, another of the Empire's troops, to find a way to stop it. The primary objective of Teppei and X is to save Teppei's brother, but as they explore more of the Area and discover more about the Machine Empire, they begin to battle for the survival of humanity. They make allies en route to the Empire's center, who aid them in defeating the empire's watchmen. The Machine Emperor finally makes an appearance once the ultimate B't has completed its transformation. Teppei and his allies face the emperor before he has a chance to meld with Raphael.