Giant Robo

 is a Japanese manga series by Mitsuteru Yokoyama. The manga, which was first published in 1967, spawned a live-action "tokusatsu" television series of the same name, as well as a series of original video animations called "".
Plot.
Part 1.
The secret society "Big Fire", scheming to conquer Earth, is furthering "Project GR". The special investigation organization of the United Nations dispatches an agent in "Country T" to interfere with the plan. Daisaku Kusama, a Japanese tourist, is mistaken for the agent and is abducted by "BF".
Part 2.
Daisaku Kusama comes back barely alive to Japan with Secret Agent Azuma with GR1. However, "BF" plans an attempt on Daisaku's life to recapture GR1 and they let GR2 and GR3 attack Tokyo.
Part 3.
A bomber carrying a hydrogen bomb crashes into Japanese waters. The hydrogen bomb has already been recovered by "BF" though the bomber is recovered at once. "BF" demands that GR1 should be exchanged for the hydrogen bomb.
Adaptations.
Adaptations include:
"GR: Giant Robo".
 is an animated TV series written by Chiaki Konaka ("Serial Experiments Lain", "The Big O") and directed by Masahiko Murata (', "Mazinkaiser") and produced by SoftGarage. The TV series is a re-imagining of Mitsuteru Yokoyama's manga and was created to commemorate "Giant Robos 40th anniversary.
"GR" premiered January 19, 2007. The series finished its run on July 6 of the same year, totaling 13 episodes, with the possibility for two further seasons. As of 2020, the series appears to have been cancelled.
The story takes place at the dawn of the 21st century, when Earth is overrun by giant robots. Daisaku Kusama encounters one of these monsters, the titular Giant Robo, in a ruin in Okinawa. Beckoned by forces he cannot understand, Daisaku is made to bond, body and spirit, with the ancient weapon and defend his homeland from the incoming evil.
A pilot for the show was made in 2005, which was a selection of scenes from the 1967 manga in animated form. Due to a change in staff at SoftGarage, the idea of a faithful adaptation of "Giant Robo" was scrapped in favor for a modern world view, not unlike that of "Neon Genesis Evangelion". The show also has elements of the Cthulhu Mythos in it, with the Giant Robos originally being ancient machines built to fight off eldritch beings known only as "The Old Ones" that threatened the sanctity of the human race.