Alien invaders take over Great Mazinger who is at the entrance of a museum next to Mazinger Z as symbols of peace. Grendizer fights the evil invaders and Great Mazinger is recovered. 

When the Vegan empire dispatches a new general to oversee the takeover of Earth, he quickly manages to capture Koji Kabuto and, learning of Great Mazinger through interrogation, quickly commandeers it from a museum where it was kept as a symbol of peace. 

It is now up to Duke Fleed aboard Grendizer to stop humanity's former defender from becoming its destroyer.

(Source: ANN)

In the mid-21st century, mankind has begun the exploration of space, and one company, Planet Catcher Corporation, has pioneered capturing asteroids and comets to mine the resources within them for use on Earth. On one such asteroid, Tortatis, lives 12-year-old Nanbu Ushiwaka - the only child ever to be born in space and survive. But survival itself is no longer guaranteed - a military satellite triggers a disaster during a operation to capture Halley`s Comet, and Ushiwaka and his fellow colonists must find a way to survive when both their country and their company abandon them. Can they escape before the nuclear reactor on the asteroid melts down? Or are they doomed to die as they lived, among the stars?

Side stories released exclusively on DVD.

Unaired episode included with the Blu-ray.