Some short synopsis quote from IGN:

"The sequel to the blockbuster action game by Tecmo's heralded Team Ninja. Gamers must guide Ryu Hayabusa on a mission to avenge his clan and prevent the destruction of the human race. Armed with an assortment of ninja weaponry, players must help Ryu skillfully maneuver through a world fraught with peril and danger. Running on an entirely new gameplay engine, Ninja Gaiden 2 evolves the action in the sequel with an auto-generation health system, new enemies and locales, and thrilling combat built upon an extensive assortment of ninja weaponry."

Some trilling images: