If you want to unlock Yami Yugi, it will take some work. If you already beat the first tourney, press down at the tournament selection list, and you should be able to get to the 2nd tourney. Beat the 2nd tourney, do the same thing, and just go to the 3rd tourney. When you beat the 3rd tourney, Yami Yugi will challenge you. Beat him to unlock him. If you do that last tournament again, Yami Yugi will be a participant in the tournament. If you want to always face him in the final round. Make sure to beat Marik first, because if Marik and Yami Yugi face each other, then Marik will undoubtedly beat Yami Yugi.