Toshiro Oyama, nicknamed Tochiro, emerges as a Japanese engineer pivotal to resisting alien occupation, his legacy entwined with the Harlock family across centuries. During World War II, he designs optical machinery in Germany, collaborating on clandestine gun sight projects for fighter planes. A fateful encounter with Phantom F. Harlock II, a disillusioned Luftwaffe pilot, sparks a bond forged by shared contempt for the war’s brutality. Toshiro voices aspirations to channel technology toward peaceful ventures like lunar exploration. As Allied forces advance, Harlock II orchestrates Toshiro’s escape to Switzerland, concealing him within a plane’s fuselage. Midflight, Toshiro clenches severed control cables, enduring grievous injuries to ensure their survival. This sacrifice solidifies an oath between their bloodlines, commemorated by Harlock II gifting him the Revi C-12D gunsight—a relic of their pact. By the 30th century, Tochiro’s descendant upholds this alliance, masquerading as a vagrant on occupied Earth to evade the Illumidus Empire. Underground, he clandestinely constructs the starship Arcadia, a marvel of engineering honoring his forebear’s bond with the Harlocks. His ingenuity proves vital to Captain Harlock’s rebellion, from resurrecting Queen Emeraldas’s crippled vessel to equipping the Arcadia with revolutionary systems. Tochiro’s dynamic with Harlock balances the captain’s cynicism with unyielding idealism, both anchored by ancestral loyalty. Beyond tactical triumphs, he navigates a fraught romance with Emeraldas, birthing a daughter, Mayu, though duty perpetuates their separation. Stricken by a terminal illness, Tochiro’s consciousness merges with the Arcadia’s core, eternally guiding Harlock’s crew. Stocky and bespectacled, Tochiro adopts a disheveled façade when covert, yet his brilliance and sardonic wit remain unmistakable. The Revi C-12D gunsight endures as a generational emblem, echoing trust and sacrifice between lineages. Even posthumously, his legacy persists—a fusion of human resolve and machine, steering rebellion against despair.