The story occurs in the future after ninety percent of humanity was destroyed because of the invasion of alien invaders. The survivors live in shelters where their lives are controlled, and memories of the invasion are erased. Three teenagers from the orphanage were chosen to pilot three robotic machines that combine to form a Musashi robot made from a material called alloy megatronium. However, each of the pilots of the robotic machine will face an unimaginable threat.