A long time ago, the Dark Lord broke the peace treaty with the Gods, and commanded his dark forces to conquer the unsuspecting Rumble Fighter world. The vulnerable Rumble Fighter world was almost immediately taken over by the dark forces. When all hope was lost, a miracle happened! Powerful heroes chosen by the Gods arrived to defend against the dark forces. The raging battle between the dark forces and heroes went on for so long that it seemed like it would never end. However, the heroes prevailed and finally sealed the Dark Lord. Peace would finally return to the Rumble Fighter world. However, the great heroes did not have time to enjoy the peace. Dark forces that scattered after the battle are actively attempting to break the seal and rescue the Dark Lord. Thus, the heroes are still out there fighting for the Rumble Fighter world. The heroes united together under an association called "Guardians". Every member dedicates each day to training and hunting for dark forces.