Five years ago, while battling an alien force known as the "Mimesis," Dannar pilot Goh Saruwatari first met Anna Aoi. Today, on the day of their wedding, the ceremony is interrupted when the Mimesis strike again. As Goh struggles in his battle against the alien threat, Anna stumbles upon a top secret robot known as the "Neo-Okusaer" and uses it as a last-resort to save her fiancee. At that moment, Dannar and Neo-Okusaer merge to become the mighty robot "Godannar."

The history is placed right after the -cliffhanger- end of Godannar when Anna looks surprised to see Mira driving the Neo Okusaer.

The year is now 2041 AD. A new enemy called Zeravire suddenly appears in the solar system, destroying all military installations it comes across. However, a wealthy man named Klein Sandman is already aware of this planned invasion and had been secretly preparing his army for battle. His trump card is Gravion, a giant robot that utilizes gravity as its source of energy. Meanwhile a young man named Eiji secretly enters Sandman's base in search for his missing sister. It is there that he meets another young man by the name of Toga... These two must now fight together with four other individuals aboard the super robot, Gravion to fend off the Zeravire threat.

After Gravion was able to use its ultimate attack, the Zeravire threat seemed to have temporary stopped. However when it rises back up all of a sudden, the Earth Gult and its trump card, the super robot Gravion, is needed to defend this world again. All this while, the EFA is planning to create their own weapons to counter the Zeravire, the Grand Trooper. Now as they attempt to fend off the Zeravire, the people of the Earth Gult and EFA must protect their future as well as confront their pasts, and unveil the mysteries of the Zeravire.