Jiro was created by Dr. Den Komyoji, and his daughter Mitsuko Komyoji, 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. Komyogi created him with a "conscience circuit" (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 to discern good orders from bad and was supposed to keep him from being controlled by Professor Gill. However, the conscience circuit was incomplete and makes Jiro susceptible to Gill's flute (which, when played, causes all robots in the area, including Kikaider, to go berserk). Kikaider, however, is capable of resisting Gill's flute playing by transforming into his Kikaider persona, and later learns to drown out Gill's commands 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.