Alternate costumes
Successfully complete the game with at least ten Fluorites found and save. Choose to start a new game and a "Shinnosuke Normal/Special" option will be available. The special version will show Shinnosuke in a panda costume with a baby panda in a front pocket clapping his hands. The panda suit will be shown in most short clips but not all FMV sequences. Press L2 to wear or remove the panda head.

Successfully complete the game with an S rank by getting most of the Fluorites. Choose to start a new game and an option for Kaede's new princess dragon design costume will be unlocked. She wears a red skirt with little wings on the back and a small tail.

Onimusha 2 FMV sequence
Successfully complete the game and save. Choose to start a new game and a "Special Report" option will be available. This allows a small sequence from the game's sequel to be viewed.

Speed trial mini-game
Collect all 20 Fluorites (blue rocks) during game play. Complete and save the game. The Onimusha Spirits speed trial mini-game will be unlocked. Successfully complete the mini-game to unlock an option to play the regular game with the Bishamon Sword, unlimited ammunition, 99 Soul Absorbers, and automatic magic regeneration.

Easy mode
Start a game and die about ten to fifteen times. After enough deaths, a message will appear, stating that a new easy mode is open. Note: You cannot achieve an S rank when playing in easy mode.

Bishamon O Flute
There are two places in there game where a very strange man hanging from the ceiling by his feet stares at you and ignores you. Later in the game, after you use the Evil Plate and open the door, he will talk to you. The man will now take you (whenever desired), to the Dark Realm. In the Dark Realm, kill monsters until two portals open; one to go up and one to go down. Keep going down to the last level (9th or 10th) while collecting all the items en route. Open the box on the deepest level to get the Bishamon O flute. Keep the flute just before the last fight with the Demon King. It is needed to get the Bishamon Sword.

Bishamon Sword
In the Demon Realm (just after you destroy the Ultimate Creation) is a save mirror and three doors. Go to the door that resembles an iron gate. It will not open at first. Use the Bishimon O flute on it and enter. Go to the Bishimon Sword jutting out of the Skull Demon wall object and take it. It is more powerful than all three of your weapons put together, and it has speed. The sword also has an unlimited supply of magic.

Fire Orb and Bow
After defeating Reynaldo (the weird squirmy thing), go to the fire to the left where the zombie eating the human was to get a Fire Orb. Before leaving to the castle, enhance the Fire Orb to level 2.To get a Bow in the castle, go to the place where the bucket is located and cut it. Go upstairs and there will be a trick crate. To open it, press Right once and X twice. Then, press Left and press X once. Next, press Right and press X once. Finally, press Left once and press X. You now should have the bow. Make sure you have normal arrows before using the Bow. You can find 10 normal arrows when you barely enter the castle and see the samurai and the kid.