Ninja Gaiden: Dragon Sword:
Successfully complete the game on the Normal difficulty to unlock Muramasa's prize shop, artwork, and the Hard difficulty. Muramasa's prize shop allows you to view intermission sequences, letters, and character files that were found during your game session. Most are unlocked during the game by shooting the birds that appear when you use the microphone when a bird sound is heard.
Successfully complete the game on the Hard (Head Ninja) difficulty to unlock the Master Ninja difficulty.
Survive the fight with Ryu, and defeat the dragon Boss on the Normal or Hard (Head Ninja) difficulty to unlock The Way Of Kunoichi difficulty. In this mode, you will play as Momiji for the entire game.
Set the system date to your birthday. When the game is started, you will hear a special "Happy Birthday" greeting when you tap the option to start the game.