Yu-Gi-Oh! Duel Monsters

Bullies often target someone frail and weak—someone exactly like Yugi Muto. He treasures his Millennium Puzzle, an ancient Egyptian artifact that was brought into his grandfather's game shop. Believing that solving the puzzle will grant him his wish, he completes the puzzle, unleashing a new personality within him, the soul of the King of Games. The new personality named Yami Yugi is the exact opposite of Yugi. Upon any injustice toward him, Yami Yugi takes over Yugi's body and forces the opponent into a Shadow Game.