When you have destroyed the Ultimate Creation in the Demon Realm choose the iron gate door when you are given the choice of three doors at the 'Save' mirror. To open the door you must use the Bishamon O flute on it. Inside you will see the Bishamon Sword jutting out of a wall object that resembles a skull. This sword has an unlimited supply of magic and is very powerful.
When you have collected ALL 20 Flourites (blue rocks) and completed the game save it and a new speed trail mini-game will be unlocked which when you complete will unlock an option to play the regular game with the Bishamon Sword, infinite ammunition, automatic magic regeneration and 99 Soul Absorbers.
Ok, you made it through all of the levels barely, well now it is time to fight the Demon Master a giant Snake.
Before you enter the Snakes layer pick up 2 flashing specs on ground they are full health potions.
Then you will see a live feed of the Snake coming down the hall, then when it comes out it talks a bit.
Ok how to beat it make sure you have gone down spiral walk way and all your swords are level 3 which if you got this far they should be, you will also have a demon sword very powerful but hard to kill snake with it alone.
You need to hit start and start with the blue sword, as magic wears out go for the red sword, then the green sword you will need to use both potions before you die.
After all swords are use up with magic then use Demon sword it will kill snake............or does it watch and see.....save your game and you will get a trailor of the 2nd version yes He is back.
Unlock Alternate Costumes: First you must complete the game and save. After that choose to start a new game and a new option, entitled "Shinnosuke Normal/Special" option will be available. This new special version will mode will put Samanosuke in a Panda costume with a baby panda in a front pocket clapping his hands.
Unlock Onimusha 2 FMV Movie: First you must successfully complete the game and save. Now 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.