未来世界，人类开始向宇宙移民，建造了名为”ネクスト”的殖民卫星，但不久地球和殖民地间的矛盾激化，人类分成ネクスト同盟军、地球政府军和地球革命组织三大阵营相互杀伐，而战争中的主导兵器则是名为”MV（Metal Vehicle）”的人型机动兵器。主人公ジェイ ストライカー原本是ネクスト同盟军的MV驾驶员，由于厌倦了战争而和其他同样厌倦战争的人一起在殖民卫星ネクスト7落草为寇，专做打家劫道的营生，有一天却卷入了神秘超兵器”S.A.C”的争夺战中。

Earth started space colonization by creating the Next Colonies. Next later rebelled, and created the Next Government. The rebellion became a war, and the multi-purpose Metal Vehicles, MVs for short, were changed for battle purposes. Meanwhile, Terra, an Earth Rebellion force, started creating more trouble for Earth. Now, a mysterious MV-like being, S.A.C ("S" for short), is loose, and Next wants it so that they can win the war. Terra's psychic leader, Hal, has been sensing "S", and wants to know more about the power it has. The future of these three groups will be up to a bunch of outlaws who live on the abandoned Next 7 colony, though no one knows that yet...