The world known as Terra, is a planet covered almost entirely by water. Living on tiny, isolated islands, the people of this world somehow manage to keep civilization alive. With the need to travel from island to island, people have invented air ships, which come in a variety of shapes and sizes. Life goes on but requires one thing to keep it that way, Quantum Refractors.

Below the surface of Terra there exists an entirely different world. This one is dark, ancient, mysterious, and inhabited by dangerous machines known as Reaverbots. The world above and the world below are linked by Sub-Gates, usually small buildings with ladders or elevators that lead down into the underground. Dangers abound in the subterranean ruins, but they must be explored, for that is where people obtain the highly sought after Refractors.

Those who dare enter the world of the Reaverbots to retrieve the Refractors, are known as Diggers. Diggers keep the world supplied with enough Refractors to keep civilization going. A Digger's means of traveling is of course by air ship, which can take them to just about any ruin in the world. However, air ships also consume the power of the Refractors and so the ravaging of the ruins goes on and on.

Eventually, there came to be people who would seek Refractors for their own profits as well as steal Refractors from other successful Diggers. These people also use air ships to travel from place to place and are called Air Pirates...

A family of Air Pirates known as the Bonnes have gone into debt in order to build themselves a massive and very impressive air ship which they call the Gesellschaft. Now they are ready to go all out and earn (steal) the money to pay it back. Teisel, head of the family, and Bon, the little brother are out scouting to locate the ruins of the Nakkai Desert. Inside the ruins there is said to be a legendary refractor called "Diana's Tear". However, just as the Bonnes are ready to conquer the ruins, they are interrupted by a flying robot.

Glyde has arrived. He works for Lex Loath, the man from whom Teisel had borrowed the money, and demands instant payment or else. Teisel tries to explain that they are about to get the big pay-off, but Glyde insists that time is already up. A battle ensues, in which Glyde emerges victorious. He then takes Teisel and Bon captive.

Back aboard the Gesellschaft, the middle child of the family, Tron Bonne, has lost contact with her brothers. She travels to their last known location in the Nakkai Desert. There she finds a few of her Servbots who were also on the mission, saddened and crying. They explain that Glyde has taken the two Bonne brothers away until they "work off" their debt.

Tron returns to the Gesellschaft and orders her forty servbots to search the ship. They find and bring to her the IOU written out to Lex Loath for 1 Million Zenny. Tron makes up her mind to go out and continue what her brothers had started. She will gather the needed money herself and pay off the debt to free her brothers.