Follow the path of the Ninja.

In a time of hiatus in a period of bitter wars and great turmoil, the Azuma ninja clan ends its year of mourning for the tragic death of Rikimaru. The land of Lord Gohda celebrates the passing of the fourth season of peace since the defeat of Lord Mei-Oh. Only the Azuma ninjas knew the truth about Lord Mei-Oh's disappearance into a portal after he was defeated. It was a secret that even Lord Gohda did not know.
 
The Azuma ninjas serve Lord Gohda with their lives and with their honor- delivering midnight messages to neighboring states and punishment in the shadows to those who turned against him. They are a feared yet unknown group, a faceless arm of justice masked in a cloud of secrets. They are his merciless force of silent assassins.

Take on the role of one of three characters. Utilize over 20 authentic ninja weapons and tools. Experience the all-new stealth attacks and enhanced fighting engine. Master new combo attacks. Earn new abilities and combos by racking up stealth kills. Play with a friend on 5 unique multiplayer levels. Complete unique mission objectives, including espionage, theft and assassination. Play through multiple game endings.  

You'll be coming back for more.

Source: Activision