It is the year 21XX. While trying to find a fossil record, Dr. Cain, a human scientist, has uncovered a capsule with a robot from the past: X. The capsule contained a warning message from Dr. Light, his creator. X's design interested Cain, and he analyzed Dr. Light's notes. Months later, Cain was able to create robots similar to X, called Reploids, and they began to be mass-produced around the world. For unknown reasons, some Reploids began to act strange and attacked humans, being labeled Mavericks. To counter any possible threat, the Maverick Hunters were formed. Sigma, an advanced Reploid, was assigned to be their leader. X also became a member of the Maverick Hunters. Time passes and the Maverick Hunters are able to keep peace, but one day Sigma himself became a Maverick, being joined by other Maverick Hunters to start a war against humanity. Although X was by nature a pacifist, he had to do something, so he joined the new leader of the Maverick Hunters, Zero, to stop the ambitions of Sigma and the Mavericks.
