Ninja Gaiden (NINJA 外伝?) is a series of video games by Tecmo featuring the ninja Ryu Hayabusa as its protagonist. The series was originally known as Ninja Ryukenden (忍者龍剣伝 Ninja Ryūkenden?, lit. "Legend of the Ninja Dragon Sword") in Japan. The word "gaiden" in the North American Ninja Gaiden title means "side-story" in Japanese, even though the Ninja Gaiden series is not a spinoff of a previous series. The original arcade version and first two NES games were released as Shadow Warriors in PAL regions.