HT Games
Modes
Two hidden modes in "Rave Master" can only be unlocked by beating the entire campaign -- one-on-two free mode and one-on-three free mode. In the former mode, you face down two enemies at the same time, while in the latter you face three. To unlock one-on-two free mode, you must play through the entire game with every character. To unlock the one-on-three version, beat one-on-two free mode using all characters and bonus characters.
Artwork
After unlocking one-on-three free mode, change the difficulty to hard and begin a new game. Choose either Haru, Musica or Elie and beat the game. Depending on which character you use, you'll unlock two pieces of artwork -- one character-based and one CGI-based. Go back and play through this mode as the other characters to unlock their specific artwork.
Character Costumes
After you've unlocked both pieces of artwork for each character, go to either free mode, versus mode or story mode. Move the cursor to the character you want to select and hold down both the "L" and "R" triggers as you make your selection, and don't let them go until the round begins. Now your character will be in his second costume. If you choose Musica, he'll have red hair and no shirt, Elie will be wearing a schoolgirl's uniform and Haru will be dressed in a Plue costume.
Reina
Turn on or restart the game. Wait for it to boot until you reach the title screen that reads "Press Start Button." Here, use the d-pad to press up, up, down, down, left, right, left, right, and then press "B" followed by "A." If you've entered the commands correctly, you'll hear a voice confirm that the character Reina is now playable. You can now select her in both free and versus modes.