Tochiro Oyama, referenced historically as Toshiro Oyama, spans multiple timelines within official narratives. His ancestral iteration, a Japanese optical machinery designer employed in Nazi Germany during World War II, encounters Luftwaffe pilot Phantom F. Harlock II as the conflict nears its end. United by their disillusionment and shared vision for technology’s peaceful potential—particularly Toshiro’s ambition to repurpose rocketry for space exploration—the pair form a bond. During a desperate flight to neutral Switzerland, Toshiro sacrifices himself by jury-rigging damaged aircraft controls with his own body, ensuring Harlock II evades Allied interception. This act forges a hereditary oath of loyalty, marked by Harlock II’s gift of a Revi C-12D gunsight, later preserved as a familial relic. Centuries later, his 30th-century descendant, Tochiro Oyama, reemerges as a Solar Federation engineer turned clandestine resistance operative. Disguised as a vagrant to avoid Illumidus detection, he covertly constructs the starship Arcadia—a namesake honoring his ancestor’s pact. His technical prowess extends to discreetly restoring advanced vessels, including Queen Emeraldas’ craft, all while maintaining an apolitical façade. The Arcadia’s design integrates the ancestral Revi C-12D as a core mechanism, symbolizing the enduring alliance between the Oyama and Harlock lineages. Tochiro’s persona marries pragmatism to idealism, employing strategic subterfuge—such as feigning vulnerability to outmaneuver adversaries—while orchestrating covert defiance against oppressive regimes. His rapport with Harlock and Emeraldas balances sardonic humor with steadfast allegiance, though tactical disagreements occasionally strain alliances. Expanded narratives, including *Endless Orbit SSX*, depict his consciousness fusing with the Arcadia’s systems, allowing posthumous guidance of the ship—a narrative choice emphasizing his dual role as engineer and eternal custodian of the crew’s purpose. Manga adaptations introduce expanded generational layers, showcasing his WWII-era ancestor’s son intersecting with Harlock II’s daughter, deepening familial entanglements. While cinematic portrayals depict Phantom F. Harlock II without an eyepatch, the manga’s inclusion of this trait remains cosmetic, leaving Tochiro’s narrative role unchanged. All iterations consistently frame him through motifs of self-sacrifice, technological innovation, and friendship enduring across eras of strife.