Don't listen to the negative reviews

Boring

It's not great by any means, but it's a pretty good movie that didn't leave me filled with regret for investing time in it.

The movie's neither hopeful in contrived ways, nor hopeless in different contrived ways. Somehow it manages to be wonderful

"Great Mazinger" is a direct sequel to "Mazinger Z", since Mazinger Z's last episode is also Great Mazinger's first. To battle a new, more powerful menace, an improved version of Mazinger, with a new pilot, is introduced. The new hero, Tetsuya, proves to be a bit of a hothead and in the end he'll need the help of Koji (the hero of Mazinger Z) so he can defeat the forces of evil. I have great childhood memories of this show : the art was inventive and the villains rather scary, at least more than in "Mazinger Z". The Mikene empire, set at the center of the earth, was populated with grotesque half-beast creatures who kept sending one grotesque threat after another. Definitely a great show, with a darker, grittier tone than "Mazinger Z".