Beat the game in any way to unlock this mini-game. You will be put into a series of rooms containing the bosses from the game. The amount of bosses depends on the difficulty you select. Harder difficulties are unlocked by beating the easier modes.

Unlock Boss Rush Mode and play it once. Reset the machine and during the Konami title screen, press up, up, down, down, left, right, left, right, B, A. Then start up Boss Rush Mode to play with the original vampire slayer! Simon is much slower and doesn't have the fancy moves that the others have. He does hit MUCH harder though, so he isn't that bad of a choice to use.

Beat the game with the best ending and you'll unlock the sound test mode that lets you listen to all the game tunes.

Get the best ending in the game. Start a new game and choose your name as MAXIM. You will play as Maxim! He is much quicker than Juste, but is more limited. He cannot equip any items at all, and is limited to his star boomerang. He can pick up Heart Containers and Life Jars though. He has a meaner dash and can triple jump. He has immediate access to the whole game, with the road barred only by obstacles that he can't get around. Theoretically you can get him to the end of the game in under an hour - easily. (He doesn't need keys, and can skip large portions of the game because of it.)

Maxim has to go around the whole castle to unlock Dracula's chambers and then must proceed there to kill the guy. It just takes some detours to get to the end.

To unlock Hard Mode, beat the game once, then enter HARDGAME as your name.

Acquire the Monster Tome relic.

To play without magic, beat the game once, then use the name NO MAGIC when starting a new adventure.