In the Sengoku period, a rōnin named Nanashi, whose name literally means “nameless”, rescues a young boy, Kotarou, and his dog, Tobimaru, from an abandoned temple. Kotarou, who has no family and is being hunted by a mysterious militia organization from China, hires Nanashi as his bodyguard. Among the militia’s members is Rarou, a highly skilled warrior with blond hair and blue eyes who follows the commands of an old man called Byakuran. Unlike his fellow militia members, Rarou is not serving any emperor; he simply seeks to challenge the strongest fighters.