Robotics scientist Ryuuichi Narasaki designed the MI-6 Miroku prototype for Martian terraforming. A catastrophic testing accident permanently altered his life, claiming his left eye and, far more traumatically, the life of his young daughter Emi. Her death resulted directly from his creation's malfunction. Consumed by guilt and shame, Narasaki entered prolonged seclusion while the Miroku unit was deactivated and stored.

Years later, when the Martian entity Negadon arrived in Tokyo and conventional forces failed, Narasaki confronted the choice to reactivate Miroku. He saw facing the monster as a final act of atonement for the past failure that took his daughter. Despite advanced age and immense psychological burden, he resolved to personally pilot the robot. He believed humanity's actions on Mars had unleashed Negadon, yet he remained determined to protect Earth.

During the climactic battle against Negadon in Earth's upper atmosphere, Narasaki deliberately pushed Miroku's reactor beyond safety limits. He executed a decisive attack, driving the robot's drill arm through Negadon's primary energy emitter. This triggered a massive explosion that destroyed both creatures. Narasaki remained aboard Miroku, ensuring the monster's defeat through self-sacrifice. His final transmission expressed his commitment to eliminate the threat as his ultimate legacy.