Roger Devlin, originally named Tochirō Ōyama, was the chief designer and builder of the starship Arcadia and the closest friend of Captain Harlock. His death from an illness preceded the main narrative, yet his consciousness endured within the Arcadia's computer, maintaining a lasting connection to the vessel.

He shared a romantic relationship with a woman called Emeralda, an early iteration of the character later known as Emeraldas. Their union produced a daughter, Mayu Ōyama, identified as Maia Devlin in the English dub. After his passing, he expressed a final wish for their daughter to stay on Earth and not become part of the Arcadia's crew.

The film "Arcadia of My Youth," released in English as "Vengeance of the Space Pirate," expanded on his backstory and friendship with Harlock, using his original name, Tochiro Oyama, and introducing an ancestral figure named Phantom F. Harlock Senior. In the American adaptation "Captain Harlock and the Queen of a Thousand Years," he was renamed Roger Devlin; this version merged plot elements from two distinct series without incorporating direct interaction between the combined casts.