Kaito, a young genius, gets sent to Mars to eradicate unknown creatures. There, the Martian Military uses puppets called Humanoid Weapons (HW) that can be controlled to fight for their cause. On Kaito's first patrol, he gets lost and finds a mysterious HW injured and left alone in a pile of rubble. But something about this HW is different... Together, they face the perils of dangerous creatures and internal conflicts as both fight to save what both care for most.