Trade & Battle: Card Hero (トレード&バトル カードヒーロー Toreedo & Batoru Kaado Hiiroo?) is a card battle RPG developed by Nintendo R&D1 and Intelligent Systems and published by Nintendo for the Nintendo Game Boy Color. It was released only in Japan on February 21, 2000. It seems that Trade & Battle: Card Hero was intended to be released in America, but it was canceled for unknown reasons (going to www.card-hero.com redirects you to Nintendo of America's home page).
In this game, the player plays as Hiro, a blue-haired boy living in a town where the game Card Hero has become very popular. He wishes to become a master of the game by collecting different kinds of cards. He also wishes to duel various opponents, including his rival, Masaru Kado. His goal becomes harder to achieve when several bad guys cause trouble in town.
Source: Wikipedia, "Trade & Battle: Card Hero", available under the CC-BY-SA License.