Two brothers race across the sky on their hover bikes when a massive metallic fortress blocks their path. A brief clash leaves the fortress mortally wounded, and it retreats, dropping the brothers into a barren wasteland. There they encounter nomadic people who explain that the fortress is actually hidden within a mountain. The nomads beg the duo to finish the job, and two of them join as guides. Along the way, the group gains the aid of a faery who can transform into a mech‑warrior woman.