Alternate costumes
Successfully complete the game under the hard difficulty setting to unlock Samanosuke's alternate costume.

Successfully complete the game with an S rank by getting all of the Fluorites to unlock Kaede's alternate costume.

Speed trial mini-game
Collect over 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. Open it to get 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.

Hint: Better gauntlet
Reach 20,000 souls and when you go to enhance you will have a better gauntlet. Go when you have 50 to get the Golden Ogre Gauntlet.

Capture 50,000 souls to get an even better gauntlet.

Hint: Great armor
There is a chest behind the waterfall containing the Great armor.

Hint: Extra red souls
When fighting enemies around the floating blue skull-ball things, allow them to absorb the souls that are released when you slay an enemy. When you kill the skull-ball, you will get many more red souls than if you had absorbed them directly from the demon.

At the end of the game, when you are walking down the spiral pit, you will reach a pink and black blob that squirts out the "squid" monsters. Stand slightly to the left of where they land. When they are getting up (low enough that they are off-balance, but high enough that your foot can reach them), kick them over and stab them when they are laying down. You can easily get your red soul bar filled up 30 times using this technique.

Hint: Easy souls
If you are low on health at the end of the game before facing the Boss go to the entrance of the keep for some battles. By now they should be easy -- just absorb the souls to raise your health

Hint: Defeating Marcellus
At the end of the game you should have all weapons and orbs at the maximum. When fighting Marcellus again, kick him and use the Thunder Orb's magic. For some reason, this is stronger than his other attacks.

Hint: Defeating Fortinbras
Start off by doing any type of attack that will make Fortinbras fall to the ground (special attacks will make this quick and easy). From this point on, just keep kicking him to death. This will take some time. You will never get hit, plus he will not be able to attack you if you can keep the chain kicks going.

Use this strategy if you have only your three normal weapons, and not the secret sword. Kick him, then slash him with the Enryuu Fire Sword. It is the strongest. Give him about five kicks and then deliver a Thunder Orb magic. Repeat this until you have no more Thunder magic remaining. Then, use the Wind Orb magic to knock him down. Use the Fire Orb and some kicks. Most of his attacks are easy to dodge, except the fire.