His creation Yu-Gi-Oh! initially started out as a manga, and the card game, Duel Monsters, was a fictional in-universe card game for the manga. It became an anime in April 1998 and the card game was de-fictionalized and made real in February 1999 by Konami, named the Yu-Gi-Oh! Trading Card Game. It has since become one of the most successful trading card games in history, selling over 22 billion cards ever since its launch.