On an archaeological mission to the end of the known universe, Professor Daiba unwitting unleashes an ancient horror from its confines. Five years later the malevolent alien force sets in motion a plan which reunites the various crewmembers of the Arcadia to sail the stars once more as well as bring Tadashi Daiba to meet Harlock for the first time (again).

Sea Pirate Captain Harlock and the errant samurai, Tochiro arrive in the United States on the Western Frontier. Along with a mysterious woman they meet along the way, the two friends challenge sex rings, bandits, and a corrupt sheriff. They are searching for a lost clan of Japanese immigrants, and they will tear Gun Frontier from end to end until they find it.

Space Symphony Maetel: Galaxy Express 999 Side Story is a 2004 anime series created by Leiji Matsumoto, and is a side story to the Galaxy Express 999 series and the sequel to Maetel Legend.