Unlockable List

How to unlock: Beat the game to unlock Zeros mini-game. A Mini-games menu should appear at the title screen and you can select it from there.

Finish all missions with 100 points: Fefnir Mini-game
Use Zet Zaber for the whole game and beat the game with S rank: Harpuia Mini-game
Finish every mission with 100 points: Leviathan Mini-game
Use the buster shot for the whole game and beat it with an S rank: Phantom Mini-game

Hard Mode
How to unlock: You need to beat the game on the normal mode. Hold the L Button and select New Game to activate Hard Mode.