A small special in which the show's stars, Drossel and Gedächtnis, explain a little bit about how the show is made, through interviews and behind the scenes shots.

A giant sea monster known as "Dragonsaurus" has emerged from out of nowhere, terrorizing the depths of the oceans. Great Mazinger, Grendizer and the Getter Robo G team join forces to combat the new threat. But their task becomes more complicated when Dragonsaurus swallows up Boss Borot and makes its way toward Tokyo.

(Source: ANN)

This is the condensed theatrical adaptation of the original TV series' first season.

Apulo (a cat-like space alien with the ability to lock a human's emotions) and Latell work for the Division of Space Piracy (or DSP for short). The two of them are extremely destructive in their solving of DSP cases. They are attempting to stop Youmei the space pirate from exploiting Computer Aided Thinking for his own nefarious plans.