Unlock Critical Mode: Beat the game on the Hard difficulty setting. In this mode only critical hits will kill enemies.
Unlock Ultimate Mode: Complete the Oni Target Practice mini game. In this mode each character will start with their most powerful weapon, 10 talismans, infinite Oni power, infinite bullets, infinite arrows and 30 medicines. Every weapon that is collected will be at it's max level.
Original Onimusha Swords: To have all three swords from the original Onimusha successfully complete the game with all the three items from the Phantom Realms or play the game with a memory card with a saved game from Onimusha: Warlords.
Bishamon Sword: To get a Bishamon sword complete the game with a Onimusha rank or get it in the Phantom Realm in Honnouji when Sam goes back to the past.
Ako's Black Haori: To unlock Ako's Black Haori successfully complete Issen/Oni training.
Unlock Alternate Ending Sequence: To view the alternative ending sequence increase all seven Haori of Ako to the maximum. To be able to do this all Kodama have to be found.