Unlock Attack Power 4
Get 1st place in Time Attack mode with any character to unlock the 4th Attack Power.

Unlock Max Difficulty:
Get 1st place in Survival mode with any character.

Unlock Rock Lee:
Complete Story mode without continuing up to the fight with Zabuza. After defeating Zabuza, Rock Lee challenges you, defeat him and the story ends after another scene. You will now be able to select him in the other modes.

Unlock Kyuubi Naruto:
When you have unlocked Rock Lee complete the game twice with every character in the 1-Player mode. When completed a message will to you to press the Z or X button during the character select screen (for ALL modes of play) when the cursor is over Naruto.

Unlock Sharingan Kakashi:
Complete the game in 1 Player mode after unlocking Kyuubi Naruto with Kakashi for the second time. A message will tell you to press the Z or X button during the character select screen (for all modes of play) when the cursor is over Kakashi.

Unlock Sound Test:
Complete the game at least once with a character not including secret characters and after obtaining ALL of their Ninja files in Single Player Sound test can be found in the light green menu 'Omake' (Extras).