Shin'ichirō Izumi commands the Daimobic Base after inheriting leadership from its late founder, Isamu Ryūzaki. Tasked with directing Earth’s defense against the Baam invasion, he shoulders operational control over the super robot Daimos. As Nana Izumi’s grandfather, he raises her and Kazuya Ryūzaki following Kazuya’s father’s death, drilling both in karate and mecha piloting—skills that propel Kazuya to become Daimos’ principal pilot. His leadership extends beyond battlefield tactics to instill discipline and ethical resolve, balancing the demands of interstellar warfare with the personal growth of his charges.

Shin'ichirō orchestrates Daimobic’s technical and strategic frameworks, aligning Earth’s military resources while thwarting rivals like General Sakamori Miwa, who covets Daimos for personal ambitions. Unyielding in safeguarding humanity, he simultaneously nurtures Kazuya’s evolution as both a warrior and a person. Their bond, forged through years of martial arts mentorship, proves vital: Daimos’ combat systems synchronize with the pilot’s movements, forging a direct link between Kazuya’s martial mastery and the robot’s battlefield efficacy.

Shin'ichirō’s story remains confined to the original series, with no documented expansions into spin-offs or alternate media.