Two brothers are riding around on their hover bikes, when suddenly a giant metal fortress gets in their way. After a brief battle, the duo manages to gravely wound the fortress. It retreats and dumps our heroic pair in a wasteland. But this wasteland is inhabited by nomads that indicate that the fortress was hidden inside a mountain. The nomads plead for the duo to finish the job. Two of the natives go with them as guides, and somewhere along the way the gain the help of a fairy that can transform into a mech-warrior woman. (Source: irreality.org.uk)

To succeed to his father, Lid Kail sets out a journey to defeat the incarnation of the evil that seems to dominate the world. Longn and Mimau also began to journey to achieve his father’s will. On their way, Key and Bagda join them. They overcome some difficulties, and finally they met Vaii, the evil. They managed to beat Vaii, but it still doesn't solve their problem... (Source: Animenfo)

Based on a 1980 manga by Mikuriya Satomi, this adaptation differs considerably from the original. The story started in its prequel was completed with this second OVA.