Austral Island is located 2,000 km south from Samoa islands. The existence of the island was removed from the official records, and Tagami Yuu made a journey to search for the reason.

He sailed for the island with Dr. Waive who was his father's friend, Doris who is the daughter of Dr. Waive, and Captain who is the friend of Dr. Waive. On their way to the island, GAIL, the international conglomerate, and gangster, Cougar Connection lead by Lady Lynx attacked them.

They managed to arrive at the island, but suddenly a mysterious monster began to attack them. When they became ready for death, a blue giant robot appeared. It destroyed the monster and saved them. Although it was an existence far beyond human knowledge, it reminded Yuu of something warm and familiar.

It was Giant Gorg which is called "Messenger of the God" by the inhabitants of the island. Escaping from the attack of GAIL's assault team, Gorg guided Yuu into the underworld. There, he found alien's relic and an alien who woke up after 30,000 years' sleep.