Jiro was created by Dr. Kohmyoji, and his daughter Mitsuko Kohmyoji, for the purpose of defending the outside world from the evils of Professor Gill and the DARK organization. He is unlike other androids because Dr. Kohmyoji created him with a "consciencecircuit" (Later identified as "GEMINI"). The conscience circuit allows Jiro to have feelings and emotions, unlike his other android "brothers", and was designed to allow Jiro develop a sense of morality to avoid being controlled by Professor Gill. However, the conscience circuit was incomplete and makes Jiro susceptible to the maddening influence of Gill's flute, unless he transforms into his Kikaider persona, before he learns to drown out the noise by emitting a high-pitched tone. Jiro also owns a guitar that he always plays to announce his presence. Mitsuko soon grows to develop feelings for Jiro and defends and repairs him whenever he is injured. Jiro, develops feelings for Mitsuko and says that regardless of his terrible past, he still wishes to be born if only to fall in love with Mitsuko all over again. He also cares deeply for Masaru and the other humans in the animation.
Kikaider is Jiro's alternate form, a powerful battle android with a "heart" who fights to protect the world from Professor Gill and the DARK organization. He has many abilities and travels around on a motorcycle named "Side Machine". His outer shell is half-blue and half-red because of his incomplete conscience circuit (if it was complete he would only be blue, as blue signifies "good" in the Japanese culture). A completed blue form of Kikaider is seen in the seventh and final volume of the manga Kikaider Code 02.