From the Official site:
Master the Ancient art of Stealth in Tenchu Z using your keen senses and wide array of Ninja weaponry to become the Ultimate Ninja Assassin. Immerse yourself in Feudal Japan as you take on more than 50 different missions to assassinate wrong doers, gather info, track enemies and collect or destroy targets. Customize your ninja by earning new costumes, accessories and power ups as you successfully complete each mission. Play solo offline or 2-4 multiplayer co-op via Xbox Live or System Link
Work cooperatively for a completely different ninja experience. Team up with a friend to finish off your foe. Let a friend subdue him from behind as you run him through with your katana.
Use sound, smell and sight to master the “Stealth Kill.” Scale walls, fly over rooftops and spring from the shadows to attack without detection as you eliminate even the toughest opponents with one devastating blow.