During a motocross practice, Keisuke Jin is ambushed by two Myth Cyborgs created by a secret organization that's attempting to control Japan, G.O.D. (Government of Darkness). He transforms into Kamen Rider X, but little does he know that his battle is recorded and analyzed by King Dark, G.O.D.'s commander, to create a super cyborg. Other G.O.D. cyborgs are attacking all over Tokyo and in the middle of the crisis, the original four Riders return to Japan from different countries around the world. The five Riders unite to lead a counter attack against G.O.D.

1962 Japanese movie

A sinister organization launches a wave of audacious attacks in an attempt to gain world domination. Commanded by the evil Professor Gill, masked androids and fearsome DARK Destructoid monsters terrorize innocent victims and wreak havoc throughout Japan. A solitary figure emerges to combat the menace. Whenever DARK attacks, a denim-clad road warrior appears, strumming a haunting refrain on his guitar. His name is Jiro, and a secret lies at the heart of his lonely existence. Jiro is a mechanical man. Vulnerable to Professor Gill's shrill flute wooing him to the DARK side, Jiro battles the evil menace by transforming into the mighty red-and-blue android known as...Kikaida.