A flying fortress appears over the town as a group of heroes called the Dragon Keepers dedicate themselves to defend humanity in a never ending war against the invaders. Thirteen years later, the fortress continues to send down monsters and creatures called Dusters to fight the Dragon Keepers every Sunday in an arena display called the Sunday Showdown. The latest is Ul-Tora Tiger, who puts up a dramatic fight against the Dragon Keepers before being defeated. However, it is revealed that this was all staged. In reality, the Dragon Keepers beat the invaders within the first year they arrived. They set up a truce with the remaining Dusters to have them put on performances like this in exchange for being allowed to live. One of the Dusters, Footsoldier D, has grown tired of this and tries to take a stand against the Dragon Keepers before being swiftly cut down by the Red Keeper. He decides to disguise himself as a human and join the Dragon Keepers so he can take them down from within.