Unlock Versus Mode: At the 'Title' screen hold L1 + R1 and press Square + Circle. If the code has been entered correctly you will hear a confirmation sound. Versus mode can also be unlocked by killing the sword smith.
Unlock All Sword Skills: In Versus mode pause the game and hold R1, then press R2(2), L1(2), L2(2). Release R1, then press R2. If the code has been entered correctly you will hear a confirmation sound.
Increase Sword Hardness: Pause the game and hold R1 + R2, then press Right(2), Left(2), Down, Up, Circle. Entering this code will make the main player's currently equipped sword increase in hardness by one. The code can be entered again until a maximum hardness of five has been reached (this code will not work in Versus mode).