After the mecha Gravion was able to use its ultimate attack, the Zeravire threat seemed to have been stopped. However, when the attacks suddenly recommenced, Earthgertz and its trump card, the super-robot Gravion, are needed to defend the world yet again. All the while, the Earth Federation Alliance (EFA) is planning to create their own weapon to counter the Zeravire, using the Grand Trooper. Now as they attempt to fend off the Zeravire, Earthgertz and the EFA must protect mankind's future, confront their past, and unveil the mysteries of the Zeravire.