A 1998 anime and the first adaptation of the Yu-Gi-Oh! manga series by Takahashi Kazuki, produced by Toei Animation. It adapts the first 59 chapters of the manga in a heavily abridged format, and is popularly known as Season Zero by fans.
The series tells the story of Muto Yugi, who after solving the ancient Millennium Puzzle, awakens a gambling alter-ego within his body that solves his conflicts using various shadow games.
The anime is notable for retaining some of the aspects of the manga, such as various dangerous and oftentimes lethal games, as well as the overall psychological horror theme the series initially had. However, the popularity of the fictional "Magic & Wizards" card game (later known within the subsequent installments as Duel Monsters) caused the series to shift its focus almost exclusively to said card game.
It spawned a short-lived card game made by Bandai in 1998, before Konami acquired the exclusive rights for the card game which later became the current incarnation of the Yu-Gi-Oh! OCG/TCG.
The anime also had a theatrical movie released in 1999, which focused on Aoyama Shougo gaining the legendary Red-Eyes Black Dragon as he learns to bring out his confidence to duel.
