Ninja Assault

You can unlock several modes simply by finishing stages in story mode with each character, so don't worry about all those blank spots!

• Clear Guren's story and unlock Mission Mode 2.

• Clear Gunjo's story and unlock Mission Mode 3.

• Clear Aoi's story and unlock Mission Mode 4.

• Clear story mode completely to unlock Mission Mode 5.

• Unlock the Final Mission by completing previous Mission Modes.
  

  Unlock More Credits

  You won't have infinite credits (unless you cheat with a Gameshark) but you can add one credit to your current maximum, up to 12, if you lose all credits in a chapter (this means you suck, BTW).
  

  Unlock Weapons

  To get the Magnum and Shotgun in story mode, do this:

• Magnum - Clear Final Mission (mission mode)!

• Shotgun - Achieve S-rank on all training missions!