Start a game and die three times. A message will appear to indicate that a new easy difficulty setting is available. Note: You cannot achieve an Onimusha rank when playing in easy mode.
Successfully complete the game under the normal difficulty setting.
Successfully complete the game to unlock the Scenario Route option, Man In Black Suit mini-game, Oni Organization mini-game, and the Puzzle Illusion Dream Dimension mini-game.
Strongest equipment mode:
Successfully complete the game under the hard difficulty setting. Start new game to begin with the Blazing Fire Sword, 20,000 in money, 30 Intense Medicines, 10 Wood, all level 3 armors, unlimited ammunition, and skill always full.
Successfully complete the Oni Organization mini-game. You must hit with a One Flash attack in order to do damage to opponents.
Puzzle Illusion Dream Dimension:
Successfully complete the game with all Paintings Of Beauties.
Successfully complete the game with the Onimusha rank.
Oyuu's alternate costume:
Get a 100% scenario completion.