Prince Richard and Prince Sablé have been rivals since they were young. When news arrives of a princess in a far-off kingdom who requires rescuing, Richard dashes off in the hopes of saving her before Sablé manages to. Left to catch up, Sablé explores the land, and soon becomes cursed, turning into a frog whenever a strange bell is heard. Sablé must remove the curse and rescue the princess.

Kaeru No Tame Ni Kane Wa Naru is an action-adventure game. The game plays in two modes: a top-down view (where most exploration and battle is done), and a side-scrolling view (where more puzzle solving is done than battles). Battling is not actually performed by the player, instead it is all automatic. If you bump into an enemy, you will see a dust cloud appear, and the pair will scuffle, with each character's health draining. Whoever loses all their health first loses the battle. Sablé can increase his battle advantage by collecting heart containers (to increase his life bar), and power ups that increase statistics like power and defense.

Another feature of Kaeru No Tame Ni Kane Wa Naru is Sablé's ability to transform into a frog at certain points in the game. This allows him to access areas that he previously could not. The main goal of the game is to conquer a huge castle, however, sections are sealed off until you complete parts of the story, allowing you to explore it in small parts at a time.