Face the Future and Fire!
One day on their way to the Ohmazan fort, Daiku-Maryu is attacked by a giant turtle beast, Domega. During the battle, Daiya and Lee try to combine Gaiking and Serpent to become Buster Gaiking, but Lee fails in the attempt.
Aired 21/01/2006EP 9 - Face the Future and Fire!
Gaiking: Legend of Daiku-Maryu
A boy, Tsuwabaki Daiya found a black fire in an ocean when he and his father were in a small boat. A big monster came out of the fire, and the father and the crews were disappeared into the sea. When he was about to become the next victim, a large mecka dragon appeared and saved him.
5 years later since then, Daiya becomes a junior high school student. A big monster reappear, and he meets the mecha dragon,"Daiku Maryu". The head of the dragon separates from the body, and it turns into the body of a super robot, Gaiking. He gets in Gaiking, fights against the monster, and beats it.
He learns that there is an enemy that plots to conquer the world, and he leaves for another world, Darius, to stop the plot.
(Source: AnimeNfo)