When you complete the game the following features will become available options. The 'Scenario Route', 'Man in Black Suit' mini-game, 'Team Onimusha' mode and Teaser FMV.

Unlock Easy Mode:
Start a game and die 3 times. A message will then appear on screen to indicate that a new 'Easy' difficulty setting is an available option (you will not be able to get 'Onimusha' rank playing in 'Easy' mode).

Unlock Hard Mode:
This mode will become an available option when the game has been completed on the 'Normal' difficulty setting.

Unlock Kick Ass Mode:
This mode will become an available option when the game has been completed on the 'Hard' difficulty setting.

Unlock Strongest Equipment Mode:
Complete the game on the 'Hard' difficulty setting and then begin a new game and you will start with ALL Level 3 Armors, Blazing Fire Sword, 20,000 in Money, 30 Intense Medicines, 10 Wood, Infinite Ammunition, and Skill always full.

Unlock Critical Mode:
This mode will become an available option when 'Team Onimusha' mode has been completed.

Unlock Mind Twister Mode:
This mode becomes an available option when the game has been completed with ALL 18 Artworks.

Unlock Jubei's Leather and Sunglasses Costume:
Collect the Fashionable Goods item and then complete the game with an 'S' rank. Then go to the 'Special Features' menu and enable the 'Extra Jubei' option to dress Jubie in his alternate costume (press L2 to toggle).

Unlock Oyu's 1970's Costume:
Play the game multiple times to get a 100% scenario completion making good alliances with ALL the sub-characters. Then when ALL the scenarios have been unlocked in the 'Scenario Route' viewer go to the 'Special Features' menu and enable the 'Extra Oyu' option to dress Oyu in her alternate costume.

Unlock Jubei Yagyu's Alternate Costume:
To get this costume you have to collect the 'Fashionable Goods' item and completed the game with an 'S' rank. When you have done that select 'Special Features' and enable the 'Extra Jubei' option and he will then be dressed in leather and sunglases which can be toggled by pressing L2. If you have the Japanese version of the game you have to complete the game with the Onimusha rank.

Unlock Oyu's Alternate Costume:
To get her 1970's style costume you have to get a 100% scenario completion which is achieved by playing the game multiple times and make good alliances with all the sub-characters. When ALL the scenarios are unlocked in the 'Scenario Route' viewer go to the 'Special Features' menu and select the 'Extra Oyu' option.