Cool Cool Bye
Genres: Action, Adventure, Fantasy
Type: OVA, Episodes: 1
Aired: Jan 21, 1986
Source: Original
Rating: R+ - Mild Nudity
Synopsis:
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)