150 years into the future, mankind has mastered genetic engineering and populated the planets of Mars & Venus by changing their atmospheres to allow for human habitation.

Current military force was very quiet until attacks on space shipping by outlaw Pirates (former inmates of penal colonies on the outer planets) greatly amplified. The Homeworlds (Mars & Venus) Congress organized a new military force to deal with the Pirate menace: the Exoforce. Using complicated "Exo-technology" (powerful armored suits that function as impenetrable outer skeletons) these brave men and women do battle with the Pirates.

Scientists experimented with the human genetic code creating "the next phase of human evolution". This new "race" was called Neosapien. The Neosapiens have an incredible intellect, need no sleep and extremely little nourishment; they are a perfect work force for the cruel environments of the Homeworlds. Neosapiens are very bitter of their role as second class citizens and soon are captivated by a magnetic leader, Phaeton. He insisted that Neosapiens were the definitive expression of intelligent life in the Universe and destined to rule all mankind. Phaeton soon planned and launched a brutal surprise attack upon the Homeworlds, and quickly conquered them while the Exoforce was occupied with the Pirates. Shortly Phaeton has complete control over the Homeworlds, and begins his plans to conquer, and eventually eliminate all natural humans.

Only the Exoforce can defeat Phaeton and stop his foolish vision. Led by Lt. J.T. Marsh, the ExoSquad battles Phaeton and his henchmen in an effort to free humanity so that all may live in equality and peace.