A comical fantasy adventure on a fight against invaders from another world. The ruler of dark world "Don Kurai," Dark, plots to dominate the human world. There is a legend about three treasures and a hero in Don Kurai, and Dark takes over one of the three treasures, a bell of copper, but a man sent other two treasures (a spear of gold and a shield of silver) to the human world. Shinnosuke falls into Dark's ...