Yuugi gets possessed by an ancient spirit and uses shadow games to psychologically destroy people who deserve it, turning a wimpy kid into something genuinely frightening when the darkness takes over. Every episode is a different game with actual stakes, not just card tricks dressed up as combat. The 1998 series commits to something darker and meaner than everything that came after it, before the franchise turned into a trading card commercial.

Yuugi Mutou is a frail boy who loves games of every kind and is often picked on by bullies. His childhood friend Anzu Mazaki sticks up for him, while Katsuya Jonouchi, usually trading barbs with his pal Hiroto Honda, keeps bringing Yuugi trouble. What Yuugi truly wants is a friend who will never betray him. Hoping it will grant that wish, he finishes the Millennium Puzzle, an ancient Egyptian relic that came into his grandfather's game shop. Solving it releases Yami Yuugi, a dark, strong second personality known as the King of Games. Whenever someone wrongs Yuugi, Yami Yuugi takes over and forces the offender into a Shadow Game, where the loser faces the darkness in their own heart. The mix is action, comedy and fantasy.