Here is the full list of all 55 Onimusha: Warlords achievements.
Unlock Samanosuke's alternate outfit.
Complete the game on Normal without enhancing swords or using Jewels.
Defeat Fortinbras.
Collect all maps.
Defeat Marcellus's final form.
Open the gate to the Demon World.
Defeat Hecuba.
Solve all number puzzles.
Solve all decoder boxes.
Obtain all armor for Samanosuke.
Enhance all orbs to maximum.
Use the Decorated Sword to enter the East Area.
Obtain all long-range weapons.
Obtain the Vision Staff.
Cut down bamboo in the bamboo forest.
Defeat Barabazuu.
Kill a demon with a battering ram.
Defeat Stylado.
Obtain the Sacred Knife.
Speak to the first and second old moth man.
Obtain the Rosary of Communication.
Unseal the path to the Keep Underground.
Obtain the Arashi.
Defeat Marcellus.
Solve the crest puzzle.
Enhance equipment at Magic Mirror.
Enter the abandoned keep.
Obtain the Kouen.
Defeat Osric.
Save a soldier under attack by demons.
Obtain the Shiden.
Use a Special Attack to kill a demon.
Use the gauntlet to absorb demon souls.
Complete the first half of the Dark Realm.
Complete the second half of the Dark Realm.
Complete the game on Ultimate difficulty.
Complete the game on Normal without using herbs or medicine.
Complete the game in less than 3 hours.
Complete the game and get an S Rank.
Complete all stages of Oni Spirits.
Obtain the Bishamon Sword.
Collect all files.
Collect all Fluorite.
Unlock Kaede's alternate outfit.
Enhance the gauntlet to maximum.
Enhance all swords to maximum.
Use Power Jewels to increase Vitality to maximum.
NEW_ACHIEVEMENUse Magic Jewels to increase Magic Power to maximum._DESC_2_7
Strike a demon with Kaede's Special Attack.
Strike Marcellus's final form with a Deflect Critical attack.
Defeat a demon by knocking it down the waterfall.
Win a power struggle with a demon.
Spot the flock of wild geese at dusk.
Find the beetle on the tree trunk.
Absorb souls from carp.