Unlock Easy difficulty:
Intentionally lose the game two times under the normal difficulty setting.

Unlock Hard difficulty:
Successfully complete the game under the normal difficulty setting.

Unlock Issen mode:
Successfully complete the game under the hard difficulty setting.

Unlock Oni Hard mode:
Successfully complete the game in Issen mode.

Unlock Ultimate mode:
Successfully complete the Oni shooting mini game. The game will start with Sam
having the Bishamon sword; Jacque having his best Oni Musou; unlimited arrows,
bullets, unlimited Oni power, thirty Medicines, and ten Talismans.

Unlock Original Onimusha swords:
Successfully complete the game with all three items from the Phantom Realms.
Then, start a new game to have all three swords from the original Onimusha.

Unlock Bishamon sword:
Successfully complete the game with the "Onimusha" rank. Alternately, get the
Bishamon sword in the Phantom Realm in Honnouji when Sam goes to the past.

Unlock Oni Musou:
Have Jacque go through the Phantom Realm in Honnouji.

Heihachi Buraiden mode:
Successfully complete the game. Heihachi (Honda) is now selectable.

Unlock Ako's Black Haori:
Successfully complete Issen/Oni training.

Unlock alternate costumes
Michelle's alternate costume:
Successfully complete the game under the normal difficulty setting.

Michelle's second alternate costume:
Successfully complete the game with an "Onimusha" rank. Alternately, play the
game with a memory card with a saved game from Onimusha Blade Warriors.

Jacuqe's alternate costume:
Successfully complete the game under the normal difficulty setting.

Panda costume:
Successfully complete secret training mode. Alternately, play the game with a
memory card with a saved game from Onimusha Blade Warriors.

Samanosuke's alternate costume:
Successfully complete the game under the normal difficulty setting with a high
score as Samanosuke. Alternately, successfully complete the game as Jacques'
alternate costume.

Ranking Mode:
Complete the game on normal difficulty. Two ranking screens will be available.
The first one displays the individual scores for each character while the second
displays an overall letter grade and any earned titles. Play Time Points

10 pts: 0-5:59
6 pts: 6:00-7:59
4 pts: 8:00-10:59
3 pts: 11:00-13:59
2 pts: 14:00-16:59
1 pts: 17:00+

Soul Points:

10 pts: 170,000+
6 pts: 145,000-169,999
4 pts: 125,000-144,999
3 pts: 100,000-124,999
2 pts: 70,000-99,999
1 pts: 0-69,999

Enemies Defeated:

10 pts:2300+
6 pts: 2000-2299
4 pts: 1700-1999
3 pts: 1300-1699
2 pts: 1000-1299
1 pts: 0-999

Crititcal Hit Points:

10 pts: 600+
6 pts: 500-599
4 pts: 350-499
3 pts: 200-349
2 pts: 50-199
1 pts: 0-49

Dark Realm Points Purple Vest, Fire Seal, Wind Seal, Thunder Seal: 10 pts.
Ultimate Whip, Bishamon Sword: 30 pts.

10 pts: 100
6 pts: 70-99
4 pts: 50-69
3 pts: 40-49
2 pts: 20-39
1 pts: 0-19

Samanosuke’s “Warlords” Weapons:To unlock the three weapons that Samanosuke wielded in Onimusha: Warlords
obtain the Fire Seal, the Thunder Seal and the Wind Seal and complete the game.
The next time the game is played through the three weapons reappear in the
alleyway where Samanosuke materializes in the present time period.

Secondary Titles
??? :Save only once during the game
??? :Score a Crirtical hit rate of 40%
??? :Complete the game in under 5hrs.
??? :Find all 23 Tengu treasure boxes.
??? :Kill more than 3000 enemies
??? :Suffer less then 5120 points of damage.

Heal Faster With White Vest
If you have the White Vest for Ako, you can make the healing process go much
faster by twirling the right analog stick as Ako is healing you. The faster you twirl,
the quicker the healing goes.

Quick Health
In the Zoo, Stand behind the panda cutout and equip the white vest on Ako and
watch your health go up quickly.

Skip Movies
Beat the games once on any level. When you replay the game and come to a
movie sequence, just press start to skip it.

Unlimited Souls
To acquire an unlimited amount of souls, after obtaining the Oni Army Orb, get to
second area. Kill off initial wave of foes, and find something to hold down the soul
absorption button. Your Oni army will continue to defeat the spawning Genma, and
you will receive all their souls. This will take some time before acquiring a large
amount.

Easter Egg: Panda Suit Photo Opportunity
In the Bolougne Zoo, just outside of the building with the air-sealed door, there is
a wooden photo shoot prop. Stand behind it and the camera shows your character
in the panda suit from Onimusha Warlords, with Ako as the baby panda!

Mini Games:

Oni Target Practice: Complete the game on a normal setting to unlock oni target
practice. Character must use guns or arrows to pick off Genma eggs that go by on
tracks.

Adventures of Heihachi: Complete the game on a normal setting to unlock this
short storyline featuring Heihachi.

Oni Training: Complete every training session and beat the game to unlock this
bonus training session.

Genma Puzzle Space: Solve every Puzzle Treasure Box in the game and complete
the game to unlock this mini-game.

Play as Gargant:
Gargant can become a playable character in Onimusha: Blade Warriors. Have a
saved game with a clear status on a memory card in slot 1 when booting up Blade
Warriors.

Puzzle Mini Game:
Complete all puzzles in the normal game.

Defeating Guard Dog:
Note: This was done under the normal difficulty setting. First, stock up on magic
for all your weapons. Then, stock up on all the Purple Souls. At the beginning,
jump behind him after he attacks. Then, just waste the magic on him. Use every
weapons magic until you do not have any more. After that, use regular attacks.
Watch out for the ice attack. Most of the time the thunder magic from him is off
target. After a few regular attacks, transform into the Onimusha and attack him
hard. However, do not use the mega attack yet. After a few attacks, just before
your magic runs out use the mega magic attack on him. If he is not defeated, then
just attack him a few more times.

Defeating Nobunaga:
When you are fighting Nobunaga when he is in his demon form, press Square(2),
Triangle. This is a great combo move, but do not overdo it with him. When you
absorb the darkness from his sword and you get it, remember that some of his
moves cannot be blocked (such as the charge and the fireball moves). You can
only block one or two. For the charge move, press Triangle at the last moment
when he is on fire and you should dodge it. For the fireball move, just have
enough space to run around.

Regain health:
Equip Ako's White Haori then stand still.

Unlimited Genma Souls:
After going through the first set of double doors where the Oni Army is fighting the
Genma, before using the Firefly to go up the short cliff, have the Genma and and
Oni Army men on the wall of the short cliff and you as close as possible to the
doors on the other side of the field. The supply of Genma infantry are infinite and
Oni Army can take care of them by themselves. While they are fighting and
nowhere near you, tape down Circle and allow the game to run. The souls will
come to you, and you can get as many as desired without interruptions from the
Genma. For a slightly faster collection, have Ako's Blue Vest equipped. Note: The
process of getting a lot of bars filled of souls will take a long time. Also, when the
soul count reaches 9,999, release Circle. This gives you an additional bar (or
perhaps more) filled automatically. Then, tape Circle again. Given enough time
you can have 99 bars worth of souls.

Bypass Dark Realms:
Any of the three Dark Realms can be easily bypassed. This requires some skill,
Ako's Purple Vest, all weapons for the character, and all weapons been completely
enhanced. Whether or not the gauntlet is completely enhanced is irrelevant.
Before entering the Dark Realm, equip either Chigo (for Samanosuke) or Hyosai
(for Jacques). The enemies that attack will appear in multiple waves. Just wait for
all enemies to appear, then execute one magic attack. Absorb all the souls that
appear. Ako's Purple Vest should allow you to do this as many times as necessary.
However, if you are fighting large demons, you may need to get up close with
either the Tenso (for Samanosuke) or the Enja (for Jacques). Note: A crucial part
of this strategy is absorbing the souls. If you feel that you need Ako's Blue Vest as
well, make sure to switch back and forth as appropriate. Also, it is much easier to
go straight for the bottom part of the Dark Realm that you are in, as the tougher
enemies are down there first. By doing this, you can use your magic efficiently on
the tougher enemies and not have to worry about the weaker ones.

The 4th 'Dark Realm':

I know it may not sound real but it is true! There is a 4th Dark Realm.

The 4th Dark Realm is inside the Oni Mansion. Once you are inside the mansion
reach the end of the maze.(Beside the protective mirror.) Hit with any of your
weapons the pink screen. Enter the small passageway where on your left is a hole
and on your right is a bundle of boxes.

DO NOT ENTER THE HOLE!

Keep pressing the X button on the boxes. After whenabout 2-5 seconds the man,
wrapped in the green material who hangs from the ceiling, shall appear. If you
press the X button on him he shall ask you if you would like to go to the Dark
Realm.

Note:

1. I have only tried this on Hard Mode.
2. The reward should help you in the next battle!
3. Obviously the Oni Mansion is only available when playing as Jacques.