Gaiking: Legend of Daiku-Maryu is a tV series anime that premiered in fall 2005.

About the production: the story comes from an original script, there are 39 episodes of about 25 minutes and its current status is "finished".

Its main genres are action, mecha and sci-fi, with themes such as Super Robot, Kids and Isekai.

On AniList, Gaiking: Legend of Daiku-Maryu has an average score of 70%, a good score, and appears on 1,864 users' lists.

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)

Official synopsis from AniList.