Tochiro Oyama, widely known as Toshiro in certain adaptations, is the childhood best friend of Captain Harlock and the genius engineer behind the creation of the spaceship Arcadia. Their lifelong friendship began in kindergarten, and together they left Earth in search of freedom among the stars. During their travels, Tochiro met and fell in love with Emeralda, an early incarnation of the character later known as Emeraldas. Their relationship produced a daughter, Mayu. Tochiro suffered from a progressively worsening case of anemia but persevered through his illness to complete the Arcadia, naming the vessel after an ancestral biplane from Harlock’s family history. He died shortly after the ship’s launch. In most accounts, his consciousness was uploaded into the Arcadia’s central computer upon his death, allowing his spirit to remain onboard as a guiding presence or emergency auto-pilot, continuing his journey alongside Harlock. His body was buried in space, and his grave is later seen on Earth. His family includes his mother, Setsuko Oyama, and his sister, Shizuku Oyama. Setsuko preserved his bullet-riddled hat as a keepsake, eventually giving it to Tetsuro Hoshino due to his resemblance to Tochiro in spirit and ambition. His daughter, Mayu, was raised on Earth according to his final wishes, with Harlock ensuring she learned of her father’s legacy. Tochiro is defined by his tenacity, love of life, and strong honor. A brilliant engineer, he designed advanced technology such as the Cosmo Dragoon handgun and engineered habitable zones within asteroids. His technical skill is regarded as among the finest in his universe. Despite his intellect, he was known for poor hygiene and a fondness for wine. In the alternate continuity of *Gun Frontier*, an ancestral version of Tochiro appears as a samurai in the American Old West, searching for a lost clan of persecuted Japanese immigrants alongside his friend Harlock. This iteration retains the core traits of determination and engineering prowess. The 2013 CGI film *Harlock: Space Pirate* offers a different backstory, in which Tochiro—also referred to as Toshiro—dies during an accident involving the Arcadia’s Dark Matter Engine, an event blamed for devastating Earth. His consciousness is still believed to have merged with the ship, transforming it into its current form.