Daiya Tsuwabuki is a boy in junior high who is known as the town liar. He claims that five years ago, he was saved by a large mechanical dragon when he and his father were attacked at sea by mechanical beasts.

Daiya's claims turn out to be true when he meets the crew of the super robot, Daiku-Maryu. Daiya joins the crew and leaves for another world to stop an ememy plot to conquer the world.