Once upon a time a village was attacked by a devil called Chaos. Jill the warrior, sworn protector of the village fought bravely and died defending the town. Jill's two son's Rios and Shun managed to survive the onslaught. Together, they trained vigorously for revenge. On the day both of them reached the age of 20, they embarked on their quest to defeat Chaos. Guess what kind of fate awaits them?