Fight as Kuroko or Mizuki (Samurai Shodown 2)
Select versus mode. Press [L1] + [L2] + [R1] + [R2] at the character selection screen. Move to the right to play as Mizuki or to the left to play as Kuroko.
Fight as Amakusa Shiro Tokisada (Samurai Shodown 1)
Use any character to successfully complete story mode and save the game. Enter versus mode, highlight the "?" on the character selection screen, then hold [L1] + [L2] + [R1] + [R2] and press [Start].
Bonus options (Samurai Shodown 1)
Use any character to successfully complete story mode and save the game. Enter versus mode, highlight the "Option" selection on the main menu, then hold [L1] + [L2] + [R1] + [R2] and press [Start].