Dr. Komyogi is an expert in robotics and has a wealthy sponsor, Herbert Gill. Gill however, is a horrible man who forces Dr. Komyogi to develop numerous robots which he plans to use to take over the world. Dr. Komyogi realizes Gill's dark ambition and secretly develops a high-performance humanoid-robot called Jiro, who looks exactly like a human but transforms into a battle robot Kikaider who has his great superpower. Komyoji leaves Kikaider with his daughter Mitsuko and then disappears.

Finally, Gill makes his move. He unleashes a robot army named Dark to dominate and control human society. Mitsuko, reading a message left for her by her father Dr. Komyogi, persuades Jiro/Kikaider to fight off Gill's terrible robots. On that day, Jiro/Kikaider's fierce battles with Dark begin!

(Source: Comixology)