A long time ago, the Caparante legend says that the Great Demon King of Sulfur who terrorized the world was exterminated by the brave Caparante and sealed in a jar. However, the Great King of Copperland Castle has opened the jar! The embarrassed king appoints his son, Prince Donba, as a brave man and sets off on a journey to exterminate the Iou Great Demon King. Donba, who has no choice but to go on a journey, first tries to get a weapon in the castle town, but he has only 300 yen in his possession...!?