Robotics scientist Keitaro Jin and his son Keisuke become caught up in the campaign of terror by an evil organization known as "G.O.D.". They are attacked and the professor's technology stolen, but before Keitaro dies, he is still able to perform surgery on his son. With the very last of his robotics technology, he transforms his son into "Kamen Rider X". To avenge his father's death and ensure the safety of the entire world, Keisuke uses this technology as he battles the monstrous minions of G.O.D.