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)

In the year 2047, mankind discovered a rare metal ore called "Gaimetal", which possessed a huge amount of energy, and mining for these strange metal ore begins all over the world. However, in 2075, humankind were been constantly attacked by Gaist, a race of metallic creatures whose bodies were encrusted with Gaimetal, thus forming the GCG (also known as "Gaist Crusher Garrison"), an organization tasked with dealing against the Gaist. In 2064, the GCG send out mankind's line of defense: the Gaist Crushers, humans who can wear a special Gaimetal armor called "Gaist Gear", and battle the Gaist,as well as the threat opposed by a mysterious organization called "Erasers".

Takes place after the final defeat of the Dinosaur Empire and the death of Musashi Tomoe in the original Getter Robo series. Dr. Saotome, creator of Getter Robo, fears that the peace the Getter Robo team has won will be short lived and that an even greater enemies would appear. Dr. Saotome's fears are justified when the militaristic Hyakki (or "Hundred demons") Empire appears, but Dr. Saotome is prepared with the creation of an even more powerful Getter Robo, Getter Robo G and a new Getter Robo base. Also with Musashi Tomoe dead, Dr. Saotome needs a third pilot which he finds in baseball player Benkei Kuruma. (Source: Wikipedia)

Itou Keita, an average guy, is shocked when he's invited to attend the elite institution, "Bell Liberty Academy." Unnerved by the mystery, he's further distracted by the school's social dynamics. In a sea of amazing young men, Keita struggles to find out what makes him unique, and how he can possibly deserve to be treated as an equal by the boys of BL. Lacking any particular ability, just why has Itou been welcomed into the privileged world of the talented and the beautiful? Along the way, he develops intense relationships with the almost everyone at school but he is terribly drawn to the friendly, over-caring but very mysterious classmate, Kazuki Endou.