Sozo Haran was a scientist living on Mars, who created a form of self-aware cyborgs (the Meganoids). The Meganoids rebelled and killed Dr. Haran and his family, except his son, the 16-year-old Banjo Haran. Banjo escapes from Mars with a super robot called Daitarn 3, built with the Mars special metals. Living on Earth, Banjo fights against the Meganoids together with his butler Garrison and the two girls Reika and Beauty, in attempt of preventing the Meganoids from converting the human race into cyborgs.