At first glance, it appears to take itself seriously: A potential pilot (Tsuzaki Aoba) with no previous knowledge of the program is brought in and has to be trained in order to defend earth against the so-called Ancient Jinki. Apparently, a typical save-the-world type mecha series. However...
Jinki:Extend's opening animation is a direct Homage to the opening for the first Mobile Suit Gundam series (0079), and there are certain Gundam-style visual cues in the mecha battles. The series also included various homages, either in the form of characters, or visual cues to several other mecha series: Neon Genesis Evangelion, Martian Successor Nadesico, even Destiny of the Shrine Maiden.
Due to this, it is difficult to say much about the anime beyond the fact that its humor lies in its complete lack of originality. Jinki:Extend might not be the "Every Mecha Show Ever" series, but it certainly hits the major ones.
The manga would also receive Darker and Edgier sequels, Jinki - Shinsetsu, Jinki - Shinsetsu - Final Episode and Jinki Extend Relation, the last of which went on hiatus after 5 volumes.
Visual Novel Developer Giga would go on to create multiple eroges in the franchise on PC, complete with art by Tsunshima himself. They include 2010's Jinki:Extend Re:Vision, a retelling of the Extend manga, 2020's Jinki Resurrection, a sequel to the Extend manga's Complete Edition, and 2022's Jinki Unlimited.
Not to be confused with Jinrouki Winvurga, his other work.
Jinki:Extend provides examples of:
- Adaptation Relationship Overhaul: The anime is the only part of the Jinki franchise to portray Aoba and Ryouhei as being strangers to one another. Any other time the two are featured together, they're Childhood Friends.
- Alternate Continuity: The Re:Vision visual novel is a retelling of the Extend manga, with Canon Foreigner Akira as the player character and manga protagonist Akao being reworked into the main heroine.
- Anachronic Order: The anime version alternates between two main story arcs set in 1998 and 2002, and also has occasional flashbacks / flashforwards to events happing elsewhen.
- Bleached Underpants: Resurrection and Unlimited both have versions released on the PlayStation 4 and Nintendo Switch that obviously do away with the explicit content.
- Expressive Hair (more specifically, Rui's hairclips, which look like crab pincers, can pince)
- Groin Attack (In the manga, one of the female characters gets wounded over there when a large, mecha-sized blade penetrates her mecha's cockpit. She survives thanks to a rescue by her teammate.)
- Improbably High I.Q.: Elny, according to side materials, has an IQ of 300.
- Loves the Sound of Screaming: Kalis in the manga. He rants about how annoyed he is that one of the girls won't scream for him while he rapes her.
- Setting Update: The original manga took place in 1988, with the Extend manga taking place in 1991. The anime, meanwhile, retells the story during the years 1998 and 2002.
- Time Skip: There's a gap of 3 years between the original manga and the Extend manga. Likewise, Resurrection takes place 2 years after the latter.