Bullies frequently pick on someone frail and weak—someone exactly like Yuugi Mutou. His beautiful childhood friend, Anzu Mazaki, is always there to defend him, but he cannot rely on her forever. Katsuya Jonouchi, who is almost always accompanied by his verbal sparring partner Hiroto Honda, does not appear to be a bad person either, even though he constantly brings Yuugi trouble. Above all, Yuugi longs for a true friend who understands him and would never betray him. Yuugi cherishes his Millennium Puzzle, an ancient Egyptian artifact that was brought into his grandfather's game shop. Believing that solving the puzzle will grant his wish, he completes it, unleashing a new personality within him—the soul of the "King of Games." Dark, twisted, strong, and reliable, the new personality named Yami Yuugi is the exact opposite of Yuugi. Whenever an injustice is done to him, Yami Yuugi takes over Yuugi's body and forces the opponent into a "Shadow Game." The stakes are high, as whoever loses shall have a taste of the darkness that resides within their own heart.