Action Replay Codes
This will unlock the EBA mode that will replace the Ouendan characters with the Elite Beat Agents.
On the difficulty selection you will see the Elite Beat Agents symbol grayed out, tap it and it will turn the normal colors meaning that the Elite Beats Agent will replace the Ouendan character during game play. Tap it again to grey it out and use the Ouendan characters.
This also unlocks Agent J and the Ramen shop cat Neko for multiplayer.
You must get the game to save data in some way to keep this mode unlocked permanently like save replay data, get a new high score, or go to the options menu.
This will max out your Kiai meter so you will never fail a stage.