During the intro screen, wait until the close up of the fighter's eyes fades out, then when the screen switches to the fighter cutting down the trees, press Select four times. You should hear a chime if done correctly and there will be three extra samurai to choose from at the character select screen.

When your opponent is about to attack and you do not have a sword, quickly press B. If timed correctly, you will be able to catch your opponent's sword with your bare hands and thrust him/her away.