Put the game disc into a PC and look for hidden .bmp images in the root directory.
Play as Kiss
Play over 12 hours of gameplay OR unlock Uon below and finish Arcade Mode with All Characters.
Play as Uon
Play over 6 hours of gameplay OR finish Story Mode with all ten characters.
Play as Burn
Unlock Uon and Kiss and finish Arcade Mode with all character including Uon and Kiss.