You'll hear a sound if you entered the code correctly

Oni One Shot One Kill
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, SQUARE, CIRCLE, SQUARE, L3, R3, CIRCLE, SQUARE.

You'll hear a sound if you entered the code correctly

Oni Change The Character
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, SQUARE, CIRCLE, SQUARE, L2, L2, L2, L2

Do not move your cursor, yet. You can hit the L2 button until you've selected your character.

Oni Extra Powerful Punches And Kicks
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, Square, Circle, Square, R3, L3, Circle, Square

You'll hear a sound if you entered the code correctly. Now when you punch and kick an enemy they'll go flyin'.

Oni Itty Bitty Characters
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, SQUARE, CIRCLE, SQUARE, L3, R3, SQUARE, CIRCLE

You'll hear a sound if you entered the code correctly

Oni Unlimited Phase Cloak
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, Square, Circle, Square, L1, R3, L2, L3

You'll hear a sound if you entered the code correctly. Now you can stay Invisible for as long as you want.

Oni Huge Characters
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, SQUARE, CIRCLE, SQUARE, R3, SQUARE, CIRCLE, L3.

You'll hear a sound if you entered the code correctly

Oni Big Head Mode
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, SQUARE, CIRCLE, SQUARE, START, SQUARE, CIRCLE, START.

You'll hear a sound if you entered the code correctly

Oni Godly Guns
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, Square, Circle, Square, L2, L2, L1, L3

You'll hear a sound if you entered the code correctly. This code will give you Unlimited Ammo and you'll never have to reload.

Oni Avoid Fall Damage
When you fall from high area you take damage. When you near the ground push L2 to do a flip. This will eliminate damage.

Oni Hard Mode
During gameplay you can press the select button and then highlight the HELP button. Now enter:
L2, L1, L2, SQUARE, CIRCLE, SQUARE, R3, L3, CIRCLE, SQUARE