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.