Completion Bonus
Complete the game using the normal difficulty setting to unlock a new costume and plasma saber. Hold down the Left trigger and select 'New Game' to use the new costume.
100% success rate. 

Unlock Very Hard Difficulty Setting
Complete the game using either the Normal or the Hard difficulty setting to unlock the Very Hard difficulty setting.

Unlock Plasma Saber Mk 2
Complete the game using the very hard difficulty setting.

Go to: Ninja Gaiden Info Page | nGaming Home Page.