Other clips seen throughout Nadesico establish the characters and setting. The main characters, and pilots of the titular robot, are Tenku Ken, Umitsubame Joe, and Daichi Akira. The characters are similar in appearance and personality to the Getter Team from Getter Robo, as well as having counterparts in Nadesico itself (most prominently Gai and the Jovian robot pilots).
Also similar to Getter is the Gekigangar robot, which is made up of three machines: the Gekiga Jet, piloted by Ken; the Gekiga Marine, piloted by Joe; and the Gekiga Tank, piloted by Akira. The names of the machines are similar to three of the component parts of Combattler V, bringing another 70's mecha anime into the influence on the series.
Like Getter, the machines assemble in three different ways to form three robots: Gekigangar III is formed with Jet as the head and torso, Marine as its waist and upper legs, and Tank as its lower legs, and is similar to Getter 1 in its preference for air combat. Umigangar is formed with Marine as the head and torso, Tank as the waist and Jet as the legs, and is the fastest, but weakest, form of Gekigangar. Finally, Rikugangar is formed with Tank as the head and torso, Jet as the waist and Marine as the legs, and is slow but has great brute strength. These last two, however, switch their best areas of battle from Getter Robo: Umigangar works best underwater and Rikugangar works more on land, whereas Getter 2 was the land-based robot and Getter 3 was for water in that series.
The villains of Gekigangar are the Kyo'akk Empire, an alien race from the "Dark String Universe" (a galaxy shaped like the infinity symbol). They are led by the Emperor Hyperion, and under him Prince Akara. Throughout Nadesico we see that Akara sends out many "mecha-monsters" to fight Gekigangar.
There are only a few major plot advancements that occur in Gekigangar, many of which are actually shown out of order in Nadesico. In one clip, a new character, Cowboy Johnny is introduced. He is from America, and pilots the "Texas Robo" machine, an obvious parody of Jack King and the "Texas Mack" from Getter Robo. Another clip features the death of Akara's sidekick, Mii-e Mii-e. Akara himself is killed later.
By far the most important plot moment in Gekigangar is the death of Joe, at the hands of Prince Akara's replacement, General Masaka. In Nadesico, seeing this scene is a major bonding moment between Akito and Gai, and it is seen and heard several times in the first few episodes.
The characters continue to watch Gekigangar past this point, though not much is known about the remainder of the series. Joe is replaced by a new character, Ryuuzaki Tetsuya, and the Gekigangar III is replaced by Gekigangar V. (Like Combattler V, the V is pronounced as the letter V; the English dub, however, referred to it as "Gekiganger 5"). Eventually, it is seen that Masaka is defeated. The final episode features a battle between the Gekigangar V (upgraded into "Spaceganger") and Emperor Hyperion, which Gekigangar is losing until the original Gekigangar III appears, piloted by Joe. With a final Super Passion Slash and Double Gekigan Fire, Hyperion is defeated. However, by this point most of the Nadesico characters have given up their fanaticism over Gekigangar; several characters criticize the ending.
The Gekigangar III OVA, "Hot-Blooded Great Battle!" includes all clips of Gekigangar shown in Nadesico, a few never-before-seen clips, and a new "movie" featuring a battle between Gekigangar III and the Super Paleolithic people who designed it. The opening mimics that of Mazinger Z Vs. The Great General of Darkness, showing pictures of Gekiganger III that children drew, and involves a similar plotline to that movie as well.
As Nadesico progresses, we find that the very reason the Jovians (who are really humans) are attacking Earth is because they believe their cause to be just and that their path is the only true righteous one as they idolize the Gekigangar anime series. Toward the end, even Captain Yurika is a Gekigangar otaku. In the end, the Gekigangar series becomes a lesson on why people should not be narrow minded and think that their point of view is that of everyone else. That their moral code is the only one. A lot of violence and death occurs as a result of the Jovian's adaptation of this point of view into their society and their leader's attempts to preserve this adapted moral code.
Episode 14 of Nadesico, Let's go with hot-blooded anime, is both a recap episode for that series and an episode of Gekigangar III. In that episode, the characters from Gekigangar watch Nadesico's recap episode and comment on it at times. Both the heroes and villains of Gekigangar draw inspiration from Nadesico for their new technologies, with Prince Akara copying the Nadesico's distortion field and Professor Kokubunji countering it with the Gekigan Flare, which he later admits was inspired by Nadesico. At the end of the episode, the Nadesico crew is seen watching the Gekigangar episode. Despite the continuity paradoxes this relationship causes, this episode is apparently canon to Gekigangar, if not to Nadesico, as Akara uses the distortion field again in the movie. The comments made by Ruri Hosino in regards to the story and how the next episode will get back on track with it at the end of the episode along with the fact that the placing of the episode seems odd giving the events in the episodes before and after episode 14. seem to suggest the Nadesico episode being non-canon at the very least.