At the Title Screen and when the text Press Start Button is displayed, press the 1 button 16 times and then press Start. This will allow you to enter one of the following passwords.

Effect	Password
Act 1: Assault	LEGND
Act 2: Smuggling	NINJA
Act 3: Skyscraper	GIDEN
Act 4: Counterattack	DRGON
Act 5	SWORD
Infinite Force	MFREE
Pause and press 1 to turn off hits	LOVER
Time	HURRY
View Credits	MONTY
View Ending	AKUSX