In Dead Rising 2: Off The Record for the PC, PS3, and Xbox 360, the Ninja Costume can make you quite a bit more stealthy. While wearing any part of the costume, you will be less detectable by regular zombies.
Wearing all four pieces of the Ninja Costume will grant you some new attacks with swords, and stacked throwing weapons will do more damage, plus they will be thrown faster than normal.
Here are the four pieces of the Ninja costume, and where you can find them, or what you must do to unlock them.
Ninja Footwear – In The Man’s Sport store in the Uranus Zone, on a rack on the left side of the store.
Ninja Hood – In Royal Flush Mall, climb on top of the phone booth on the second level and climb up onto the next ledge. Run to the end of the ledge and jump to the next ledge. Turn around and jump and climb up to the flower box, then jump to the next ledge. Walk into one of the open windows and you’ll find the Ninja Hood sitting on a box on your left.
Ninja Mask – At the entrance to Shoal Night Club in the Yucatan Casino, go up the escalator and through the long hallway, then turn right and jump over the counter and you’ll see the Ninja Mask on a mannequin in the corner.
Ninja Uniform - Unlock the Elite Killer achievement / trophy by killing 1,337 zombies.