Collect the following amount of Golden Scarabs during the game and then trade them at the Muramsa shops for the corresponding item.

Unlock Technique Scroll - Counter Attacks:
Collect 1 Scarab.

Unlock Technique Scroll - Izuna Drop:
Collect 5 Scarabs.

Unlock Technique Scroll - Guillotine Throw:
Collect 10 Scarabs.

Unlock Windmill Shuriken:
Collect 15 Scarabs.

Unlock Wooden Sword:
Collect 20 Scarabs.

Unlock Dabilahro:
Collect 25 Scarabs.

Unlock Armlet of Celerity:
Collect 30 Scarabs.

Unlock Spear Gun:
Collect 35 Scarabs.

Unlock Armlet of Benediction:
Collect 40 Scarabs.

Unlock Armlet of Fortune:
Collect 45 Scarabs.

Unlock Plasma Saber Mark II:
Collect 49 Scarabs.

Unlock Dark Dragon Blade:
Collect 50 Scarabs.

At the 'Mission' mode screen press Up, Down, Left, Down, Right, Up, Square to unlock 5 extra missions (these missions are also in the 'Collectors Edition').

Unlock Difficulty Settings
Beat the game on any difficulty to unlock a harder difficulty setting.

Unlock Ninja Dog:
Die 3 times

Unlock Hard Mode:
Beat the game on Normal difficulty setting.

Unlock Very Hard Mode:
Beat the game on Hard difficulty setting.

Unlock Master Ninja Mode:
Beat the game on Very Hard difficulty setting.


Golden Scarab Rewards
Collect the following amount of hidden Golden Scarabs and the shop owner (Muramasa) will reward you with items and weapons that will help you in the game (when you play as Rachel there are NO Golden Scarabs).

Unlock Life of Gods:
Collect 1 Golden Scarab

Unlock Armlet of Potency:
Collect 5 Golden Scarabs

Unlock Lives of the Thousand Gods:
Collect 10 Golden Scarabs

Unlock Plasma Saber MkII:
Collect 50 Golden Scarabs

Unlock Spirit of the Devils:
Collect 15 Golden Scarabs

Unlock Dabilahro:
Collect 20 Golden Scarabs

Unlock The Armlet of Celerity:
Collect 25 Golden Scarabs

Unlock The Armlet of Benediction:
Collect 30 Golden Scarabs

Unlock Great Spirit Elixir:
Collect 35 Golden Scarabs

Unlock Armlet of Fortune:
Collect 40 Golden Scarabs

Unlock Jewel of the Demon Seal:
Collect 45 Golden Scarabs

When you have successfully beat the game on the following difficulty settings the corresponding costumes are unlocked.

Unlock Classic Ryuken Costume:
On Normal difficulty setting beat Story mode.

Unlock Ashtar Ryu Costume:
On Hard difficulty setting beat Story mode.

In Story mode successfully beat 'Normal' difficulty setting to unlock 'Mission' mode.