After beating the story Western Warriors
To unlock Keiji, beat Wester Warriors with Magoichi or Okuni (I did it with Magoichi.) After beating it a screen will come up and ask if you want to save the game after that screen it'll say what you unlocked and thats how you unlock Keiji.
Up, Up, Down, Up, Right, Left
#1 : At the main menu, enter the following on the D-pad to unlock a secret costume: left, left, up, right, right, up, left. To activate this code you must use it every time you start the game.
#2: The second costume code is when you're at the main menu, enter right, right, down, left, left, up, right.