GR: Giant Robo is a tV series anime that premiered in winter 2007, produced by A.C.G.T..

About the production: the story comes from a manga, there are 13 episodes of about 25 minutes and its current status is "finished".

Its main genres are adventure, mecha and sci-fi, with themes such as Conspiracy, Lost Civilization, Foreign and Super Robot.

On AniList, GR: Giant Robo has an average score of 63%, an average score, and appears on 2,338 users' lists.

The year is 20XX. Mysterious huge robots called "Giant Robo (GR)" started to appear all over the world and destroy cities. The earth was covered with fear. And their next target is Japan! The hero of this animation Daisaku Kusama, who works in a diving shop, encounters a mysterious girl, simply called V who leads him to make a contract with an enormous robot "Giant Robo 1 (GR1)" at the ancient ruins (Minami Yonaguni Island) in Okinawa. He made a contract with UNISOM (main organization) and was approved to be a commander of GR1. Thus his battle has begun against GRO (antagonist organization) and creates a lot of dramas. Before long, Giant Robo of the 21st century will ask the world the true meaning of its power. (Source: AniDB)

Official synopsis from AniList.