Dr. Kohmyoji is a scientist and an expert in robotics, who is being kept prisoner by the evil organization, DARK. Dr. Kohmyoji creates Kikaider in order to protect his children from Professor Gill. When Gill, the head of DARK, learns about this, he sends his androids to deal with Dr. Kohmyoji. Jiro (Kikaider) is able to rescue Dr. Kohmyoji's daughter, Mitsuko, but a fire separates him from Dr. Kohmyoji. Jiro is able to destroy Gray Rhino King, but is unable to locate Dr. Kohmyoji, who is wandering away with amnesia.

Naoto Tamura, a new detective in Central City, is killed by a Bionoid Monster in the line of duty. Doctor Kenzo Igarashi, a man whose experiments had been responsible for the Bioron syndicate's existence, brought the man back to life as a cyborg detective, Jiban.