Tochiro Oyama originates from "Arcadia of My Youth," appearing across Leiji Matsumoto's interconnected works. His background involves reincarnation, tied to a World War II-era ancestor, Toshiro Oyama. This Imperial Japanese Navy exchange technician worked in Germany, developing gun sights for fighter planes. He sacrificed himself to save Phantom F. Harlock II during an escape to Switzerland, forging an eternal bloodline pact between their families. Physically, Tochiro possesses a short stature and stout frame. He wears large round glasses that perpetually obscure his eyes and sports shoulder-length wavy hair. His typical attire is a worn brown poncho and a bullet-riddled hat, later inherited by others. His personality blends unwavering optimism with profound tenacity. He refuses to compromise ideals or betray allies, despite frequent humiliation in confrontations. He exhibits deep love for Earth and humanity's potential, even amidst disillusionment with societal decline. He values leisure and humor during crises, maintains poor hygiene, and enjoys drinking. Tochiro's engineering genius is unparalleled. Working with minimal resources, he secretly designed and constructed the space battleship Arcadia. He incorporated advanced technology like Dark Matter armor and a galleon-inspired stern. He also forged powerful weaponry such as the Cosmo Dragoon pistol and the Gravity Saber. His skills extended to constructing habitable artificial environments, notably a mobile beach within an asteroid. Despite myopia limiting long-range combat effectiveness, he mastered close-quarters fighting with the Gravity Saber, matching Emeraldas' prowess. His relationships define key narrative arcs. His bond with Captain Harlock transcends friendship, described as a union of "one body and one soul," with both willing to die for the other. Their dynamic contrasts Harlock's stoicism with Tochiro's emotional expressiveness. He harbors romantic feelings for Emeraldas, impressing her through repeated self-sacrifice despite initial awkwardness. They conceive a daughter, Mayu, though their lifestyles prevent a lasting union. Tochiro's legacy persists beyond death; his consciousness is uploaded into the Arcadia's systems, allowing him to guide the ship and assist Harlock as a spectral presence. In various timelines, Tochiro dies from illness or "space sickness," often concealing his declining health to complete crucial work. His deaths profoundly impact Harlock, who dedicates himself to honoring Tochiro's hopes for Earth and humanity. His influence ripples to characters like Miime and his orphaned daughter Mayu, symbolizing enduring hope across generations.