You do not need to pull out your weapons to perform a stealth kill. Run to the enemy and press Attack. Your weapons will instantaneously be drawn out, and you will perform the stealth kill.
Copy Missions from Cd in Mission Editor
At mission settings menu, hold Circle and press Up, Up, Down, Down, Left, Right.
Easy kills
Hit an enemy who is not aware of your presence in the head with a blow gun dart to automatically kill them.
European castle in mission editor
Successfully complete the game with all three characters.
Get Tatsumaru-without beating game
At the level select screen, hold Square + Circle and press R1, R2, L2, L1, Up, Down, Left,Right, Select. This code is the Alternate way of getting Tatsumaru without having to beat the game with Ayame,and Rikimaru. (if there is a problem,Try putting in the level select codes in for each Character first, then this code, I put it in after that, but it may work without it)
High jump
If you are in certain levels (Quarantine Village, Laborers), you do not need a grappling hook to get on to the roof of a house. Run up to the wall, face it, and jump. Your character will jump twice the normal height of the usual jump and land on top of the roof without hanging on the side.
Increase Item Inventory by 1
At item selection screen, hold R1 and Square and press Right, Down, Left, Up.
Level select
At the map screen, hold R1 and press Up, Down, Square, Up, Down, Square, Up, Down, Square, Down, Up, X.
More options in mission editor
Simply advance in the game to get more options in the mission editor. As your character reaches new levels with new tilesets, the same tileset will then be available in the editor.
Office tileset
Enter the mission editor and select "Edit Mission". Highlight the "New Mission" selection, then hold L2 and press Circle, Square, Left, Right, Circle, Square. If you entered the code correctly, you will hear a sound.
Play as Tatsumaru
Successfully complete the game with both Rikimaru and Ayame.
Regain health
Pausing the game and holding square, and then pressing Left, Right, Up, Down will restore your health.
Show Entire Map
During the game, hold select to view the map and press Circle five time.
Stealth kills
You can get the different stealth kills by being in the correct position in relation to the enemy.
Easy stealth kills
Sneak up from behind.
Sneak up from behind and crouch.
Jump on enemy, while pressing Attack in mid-air.
Moderate stealth kills
Sneak from the side.
Hard stealth kills
Sneak from front (or wait for them to turn around into you). This must be timed perfectly.
Unlock All missions in Mission Editor
At Custom Mission screen, hold R2 and Circle and press Up, Down, Down, Right, Left, Left.