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)

Picture dramas included with the first and third limited edition DVD volumes.

"This Anime (Episode 2, to be exact), where Rockman travels from the Game-World to the real world, to learn some cultural differences about Japan, was intended to be a Special Episode for the original Mega Man Cartoon Series by Ruby-Spears, which aired around 1995 in the US. As it seems, the special was finished before Ruby-Spears decided to redo their whole show with a completely new design, better suited for American audiences. Thus, not fitting the new style anymore, it never was included in the series. Still, two more episodes about the same story were produced a bit later, this time under the main title "Rockman" (unlike Episode 2, where he's called Mega Man, even in the japanese dub). It's unknown if these 3 Episodes ever saw an official release, until 2002, when Capcom of Japan decided to finally (re)release them on DVD for Rockman's 15th Anniversary (all featuring a Japanese and English dub, but no subs). It's unknown if there are any more secret animated works of the original Rockman game-series."

A pair of researchers stays behind on their dying planet of Eltria with their two daughters, Amitie and Kirie, in hopes of finding a way to revive the planet. But when the husband Granz falls ill it seems their dream of reviving the planet will die. Against her older sister's wishes, Kirie sets off with her childhood friend Iris to seek help from a distant alternate world. They arrive in Japan on Earth to search for the key to their planet's regeneration. There, they meet Nanoha, Fate, and Hayate.