Falling

It was the year 2023. Aliens attacked Earth and caused a worldwide fallout. Humans, forced underground, built an underground home, and a plan for war. Once they reemerged one hundred years later, they had created weapons, transportation finally adequate for space-travel, and an army of trained soldiers for the upcoming onslaught.
In 2125, two years later, the war is raging between the enemy aliens, the Alliance, and the Corps, or the Inter-Galactic Corps. Other alien races have also aided and joined the Corps, their mission being to put an end to the rising tyrants.
Meet squad 601, one of the Corps' best. They have been causing a recent streak of victories against the Alliance, especially after finding a major headquarters and factory on Oxium. But, while going from planet to planet, they soon discover they aren't the only ones who have suffered from the criminals, and by comparison, the humans had gotten off easy.

But that's only the beginning.

(Note: Story mostly follows Ada)