Dr. Komyoji, a brilliant robotics professor, invents Jiro, a humanoid robot capable of transforming into Kikaider. Programmed to safeguard Dr. Komyoji's children, Masaru and Mitsuko, Jiro possesses a conscience circuit enabling him to feel real emotions and discern morality. However, Jiro faces a dilemma when the nefarious Dr. Gil seeks to recruit him for his conquest for global supremacy, putting Jiro in a moral quandary as he must protect his young charges from this malevolent threat.