Super Heavy God Gravion

The current year is 2041 AD. Zeravire, a brand-new foe, arises out of nowhere in the solar system and begins destroying every military facility it encounters. But a wealthy guy by the name of Klein Sandman has been clandestinely assembling his army and has knowledge of this impending invasion. Gravion, a massive robot that draws energy from gravity, is his main weapon. In the meantime, a young man by the name of Eiji sneaks inside Sandman's stronghold to look for his lost sister. He meets another young man there by the name of Toga there. These two must now engage in combat alongside four other people on board the powerful robot Gravion to repel the Zeravire attack.