Before the time of plants and animals, Earth was completely dark and inhabited by beings we now call 'monsters'. When some voice said 'Let There Be Light' , many monsters died because they could not live in this new light world. Not all died however; some of them hid in caves, and grew stronger. Now, they want to return to the world.

Corona is a boy from Soleil Town who just turned fourteen and has to undergo a series of trials to become a true swordsman. However, soon he finds himself in a strange predicament: unable to speak to humans any more, he learns to communicate with animals, and realizes that not everything in the world is as simple as it looks.

Crusader of Centy is an overhead action game with light role-playing and puzzle-solving elements, similar to Zelda games. The game's stand-out feature are animal companions. various animals are met by Corona during the course of the game, and can be "equipped" to grant him new abilities: for example, a penguin will add an ice attack property to his sword, etc.