Tsuwabuki Sanshirou, a professional baseball player, hurt his dominate arm by the attack of monsters sent by the Black Horror Squad of Zeller, and he quitted baseball. He was recruited by Dr. Daimonji, and he saw the members of Combat Force that protected the earth and the large parent ship, Daiku Maryu (Great Sky Dragon). He potentially had special natural power, and joined Combat Force. He become a pilot of the large robot, Gaiking, and fought against the Black Monsters of Zeller.

Source: AnimeNfo

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Alternative version: Gaiking: Legend of Daiku-Maryu
Other: Toei Robot Girls
Other: Robot Girls Z