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.
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.
Easy mode
Start a game and die about five times under the normal difficulty setting. 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.
Extra Souls
Purposely let a demon get a green soul, and then kill it. It will make the demon drop more souls for you to absorb.
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.
How To Kill The Demon Doll Ayame
To kill the demon doll Ayame you first need to beat the oni spirits mini game. Then you start a new game on ultimate mode with the bishamon sword. Find Ayame the demon doll and swipe at her with the bishamon sword.
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.
Unlock Difficult Mode
Defeat the game in under three hours to unlock Difficult Mode.
Unlocked Chest Open Jewels
South Area Map
Level 1: 1-3-6
Level 2: 6-1-4
West Area Map
Level 3: 5-7-2
East Area Map
Level 4: 3-6
Get it Jewel
Your Grade
Genma Onimusha allows you the opportunity to rate your progress, based on a series of points. The perfect score is 30, meaning you have to score all available points in three categories:
Time taken to complete
Up to 3 Hours= 10 points
3-4 Hours= 7 points
4-5 Hours= 5 points
5 or more Hours=3 points