The series takes place in 16th-century feudal Japan. The original story (Stealth Assassins) revolves around two ninjas, Rikimaru and Ayame, who have both been members of the Azuma Ninja Clan since childhood. The two ninjas serve the benevolent Lord Gohda and work for him as his secret spies to root out corruption and gather intelligence in his province. However, the evil demonic sorcerer Lord Mei-Oh sought to destroy Lord Gohda, and using his demon warrior Onikage, wreaked havoc throughout Lord Gohda's province. Although Lord Mei-Oh was killed in the first game, Onikage appeared in all subsequent games as the archenemy of the two ninja, especially Rikimaru. Another major character who shows up frequently is Princess Kiku, Lord Gohda's daughter who often needs to be saved.
