on the first level after the bridge you'll see your second enemy, let them kill 3x on (5x cuz some people said that you need to die 5x but is not 5 only 3 ok) after the you die theres a message saying that you unlock the EASY MODE, there..

Get Bishamon Sword:
Fight through all 20 levels of the Dark Realm. Kill all of the monsters on the 20th level, then open the treasure box here to discover the Bishamon Ocarina. Then, in the area just beyond the second Marcellus boss fight, use the Ocarina on the bone door here to open it. Then head inside and claim the prize, a sword with unlimited magic which will kill any non-boss character in a single swipe. A powerful ally, indeed.

Unlock Difficult Mode:
Defeat the game in under three hours to unlock Difficult Mode.
Second Costume:
To unlock Kaede's second costume, a sort of demon dress, collect all 30 Flourites.
submitted by IGN Guides

Unlock Oni Spirits Mini Game:
To unlock the Oni Spirits mini game, collect 20-29 pieces of Flourite. A new mini-game will be available at the start menu.

Unlock Samanosuke's Second Costume:
To unlock Samanosuke's second costume, beat the game once on Difficult.
submitted by IGN Guides

What's 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

Number of demons killed

0-399= 3 points

400-499= 5 points

500-599= 7 points

600 or more= 10 points

Number of souls collected by the gauntlet

0-34,999= 3 points

35,000-44,999= 5 points

45,000-54,999= 7 points

55,000 or more= 10 points

The points add up as follows:

0-9= D

10-17= C

18-24= B

25-29= A

30= S

Difficult Mode Beat game in under 3 hours

Easy Mode Die 5 times on Normal

Kaedae's 2nd Costume Get all 30 Flourites

Oni Spirits Minigame Get 20-29 Flourites

Rank of X Defeat game in Difficult mode, no

Bishamon Sword, get Ogre Armor, with an S ranking

Samanosuke's 2nd costume Beat game on Difficult

Ultimate Mode Complete Oni Spirits minigame

Ultimate Mode for Hard difficulty Beat game on

Hard Mode with a ranking other than S

first get all the swords (you have to) then enhance Raizan and Enryuu to lvl3 and Arashi to lvl2 or you won't stand a chance,then save your game near the rope ladder you climbed down. Head to the well where you found the ladder and talk to the creepy man and he'll tell you about the dark realm.If you enhanced your swords it shouldn't be too hard,like i said save because its about 25-30 floors.the last floor holds the bishamon ocarina.play the ocarina in the next room after your battle with that really fast guy and enter the hand door and press a infront of that hanging body.Vwalla!!!! you have a sword that kills most demonds in 1 swipe

Battle through the Dark Realm that has ten levels. (Not to be mistaken with the Dark Realm that contains twenty levels) Upon completion of the tenth level, open the chest to get the ''Secret Key''. Take the key to the area with the Red Minotaur boss fight. Use the key on the large door marked with a plus sign to enter an area that leads to the Ogre Tower. Once inside the Ogre Tower, enter the portal in the middle of the room. Defeat the enemies on each of the 6 floors, to unseal the next portal. When you return to the main level of the tower, give your souls to the glowing statue to unlock the corresponding portal. Repeat this process for the remaining statues. On the 5th and final portal, you must face a boss on the final floor. Defeat him to gain the ''Ogre Armor''

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