A little girl named Sayoko witnesses the murder of an Interpol agent by the G.O.D. kaijin Hercules. Keisuke Jin saves her before Hercules disposes of her. Sayoko tells Keisuke that G.O.D. is targeting an important official named Kibara. Kamen Rider X has his hands full when G.O.D abducts Kibara and takes Sayoko and her mother hostage.

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.