As soon as you finish a mission, enter the Powerup screen and enter the following:
Triangle, [psx:Triange], Circle, Square, Circle, X, X, X, Circle
Enter the following code during gameplay:
L1, L1, Triangle, Square, L2, L2
Play Dante's mission 1, then save the game. Reset the PlayStation2 and wait for the Press Start button message to re-appear, then press Click Left Analog Stick, Click Right Analog Stick, L1, R2, L2, R2, Click Left Analog Stick, Click Right Analog Stick.
Press Start to return to the main menu, then choose the Load game option, press L1 or R2 to access the new costume, then load a game to play the bonus level.
Pause the game and enter the following:
X, Circle, Circle, Circle, X, Triangle, L1, R1, X, Circle.
Successfully complete missions 1, 2, or 3 while using at least one continue. At the start of the next mission, there will be an option to change the game to easy mode. Note: Once easy mode is activated you cannot return to normal mode.
Legendary Dark Night Mode
Successfully complete Hard mode to unlock Legendary Dark Night mode.