Kaeru no Tame ni Kane wa Naru (カエルの為に鐘は鳴る?, lit. "For the Frog the Bell Tolls") is an action role-playing video game developed by "Team Shikamaru" of Nintendo's Research and Development 1 division, in cooperation with the external company Intelligent Systems. It was published by Nintendo for the Game Boy and released in Japan on September 4, 1992. The title is a play on Ernest Hemingway's famous novel, For Whom The Bell Tolls.
In a land far away, the two princes- Richard (of the Custard Kingdom) and the game's main protagonist (prince of the Sabure Kingdom) have shared a friendly rivalry since they were small children. They often compete, although it usually ends in a tie or close win. In Fencing however, Prince Richard is always the victor. One day a messenger arrives from a small neighboring kingdom, warning the princes that the evil King Delarin has invaded the Mille-Feuille Kingdom and captured the beautiful princess Tiramisu. In yet another boastful attempt to best the Sabure Prince, Richard grabs a boat and rushes towards the kingdom. The Sabure Prince is left trying to catch up. While on his journey, he and Richard (and many others) are transformed into frogs in an attempt to reveal the true happenings in this kingdom.
Source: Wikipedia, "Kaeru no Tame ni Kane wa Naru", available under the CC-BY-SA License.