Unlock Yamazaki
Successfully complete the game as Ryo under the very hard difficulty setting in single mode to unlock Yamazaki.

Extra Strikers
Successfully complete the game with any team to unlock K', Maxima and Vanessa at the bottom of the character selection screen.

Fight as Iori
Successfully complete the game with the Hero Team.

Fight as Geese
Successfully complete the game with the Fatal Fury team.

Alternate costumes
When selecting a character, press L (clone costume of your enemy if you are fighting yourself) or R (different costume).