Yugi and his best friends take a break from perfecting their dueling skills to watch bug duelist Weevil Underwood and dinosaur duelist Rex Raptor compete in the Duel Monsters Regional Championship. When Yugi opens a package from Duel Monsters creator, Maximillion J. Pegasus, Yugi is forced to face him in the mysterious Shadow Realm, where all the monsters and magic are real. Upon defeating Yugi, Pegasus magically claims the spirit of Yugi's Grandpa via the strength of his strong Millennium Eye. Yugi must travel to the Duelist Kingdom and win Pegasus' tournament if he is ever to see his Grandpa alive again.