Hades Project : Zeorymer (Vols. 1 & 2)

Eight massive robots conquer Earth and set out to rule with an evil iron fist. Fortunately, rebels manage to steal the most powerful of the robots, along with the embryo of its artificial pilot. Fifteen years later, the artificial embryo has grown into the teenager Masato Akitsu, who soon learns that it is his destiny to pilot Zeorymer, the giant robot and to rescue the Earth from the seven evil mechas.