Ninja Gaiden Shadow (aka. Shadow Warriors) is actually a licensed GB port of Shadow of the Ninja on the NES console. Because of this, it is fairly faithful to the original despite starring Ryu Hayabusa, the main character of the Ninja Gaiden series.
In this Gaiden of a gaiden, Ryu Hayabusa manages to defeat Emperor Garuda and save mankind in under 12 minutes, notwithstanding running slower than in other Ninja Gaiden games.