In the near future, the “ARK Project” has initiated a program to increase the quality of human life through the peaceful use of robots. Dr. Komyoji, the chief scientist on the project, has developed a process to create a robot with a figurative human “heart” through the installation of a “conscience circuit”, but his plans are violently opposed by researcher Gilbert Kanzaki. When Dr. Komyoji is killed in an apparent accident, his children Masaru and Mitsuko are targeted by mysterious forces within the ARK Project looking to gain control of the scientist’s research data. But the villains are opposed by Jiro, the android with a human conscience who fights for justice as the hero Kikaider..