If you have a CD based system play Ys Book I & II.
Probably stating the obvious here, but CD based games have no region lock out, but HuCards do.
If you have a Duo, Duo-R, or Duo-RX system you will need the Arcade Card Duo to play ACD games, and regular CD-ROM Units need the Arcade Card Pro.
If you have a CD based system play Ys Book I & II.