Koujiro Hachijima pilots Mechander-2 as one of three core operators of the titular robot. Defined by a pessimistic outlook and volcanic temper, he routinely clashes with teammates, dismissing idealism as naive folly in their desperate war. This hardened worldview originates in personal loss: a loved one’s death during the Doron Empire’s invasion ignited his vengeful resolve, compelling him to join the resistance.

His partnership with co-pilot Jimmy Orion thrives on friction—a clashing yet codependent rapport fueled by opposing philosophies. While both fight to defend Earth, Koujiro’s cynical pragmatism collides with Jimmy’s bold optimism, sparking heated disputes. Their rivalry erupts into violence when Koujiro accuses Jimmy of prioritizing heroics over team survival.

Though primarily a warrior, Koujiro gradually serves as a grounding force against Jimmy’s riskier tactics, even as his own trauma and thirst for retribution persist. The cataclysmic mid-series destruction of Mechander Robo tests his adaptability, forcing him to master its reconstructed four-unit form—a testament to his tenacity amid shifting warfare.

No expanded appearances or narrative developments beyond the 1977 series are documented.