When an ancient, and rather large, idol, called the Devil's Whistle is removed from its resting place on Wester Island, the monster Jiger emerges from her slumber and is soon attacked by Gamera...for relatively unknown reasons, to be perfectly honest. After defeating Gamera, Jiger makes her way to Osaka, Japan, where the idol is being held at the World Expo. Jiger destroys everything in her path, both before and after arriving in Osaka, until Gamera returns for a rematch. Gamera is once again defeated when Jiger injects him, via her barbed tail, with an embryo of hers. Gamera soon falls into the bay unconscious, and it is up to two young boys to take a small submersible into Gamera's body and destroy the embryo, in the first onscreen act of abortion ever seen in a giant monster movie. After discovering that the baby Jiger has a weakness to radio waves, it is discovered that the idol, which the adult Jiger has finally reached and has buried under tons of rubble, is hollow and channels air and wind through it at a frequency that harms Jiger. After Gamera has been revived, he battles Jiger a third time. This time, however, Gamera is wise to Jiger's tricks and soon defeats her when he stabs her in the head with the idol. The movie ends after Gamera flies away.
Gamera vs. Jiger, when compared to the other films after Gamera vs. Gyaos, is actually one of the more mature films in the Showa Gamera series. Its child protagonists are almost teenagers, and thus older than every other child seen in a Showa Gamera movie, and they aren't annoying either...well, they're nowhere near as life-threateningly stupid
as the boys from Gamera vs. Viras and Gamera vs. Guiron, or as annoying as the children from Gamera vs. Zigra. The music in this film, while nowhere near the level of the first three movies, is somewhat more tolerable than usual, although the Gamera Song is still as grating as ever.
This film contains examples of the following:
- Brown Note: The statue, or Devil's Whistle, makes a lot of people sick, and it harms Jiger.
- Darker and Edgier: Not to the extent of Gamera vs. Barugon, but definitely when compared to the two previous films and the two succeeding ones.
- Evil Genius: Jiger is quite genry savy and seems to have more creative ways of trying to finish Gamera instead of simply 'more sonic beam/more ice/more knife-head!'
- Family-Unfriendly Violence: Let's see...Gamera is stabbed in the limbs by Jiger's spear...things, Gamera is impregnated after being stabbed by Jiger's tail, an act of Giant Monster Abortion (which should totally be the name of a rock band) is shown onscreen, and Gamera stabs Jiger in the head with the idol.
- Fantastic Voyage Plot: The two boys pilot a small submersible inside of Gamera in order to kill the baby Jiger.
- Friend to All Children: Unless they happen to be parasitic monsters injected into you by your opponent, however, in what may be one of only two aversions in the Showa Gamera films.
- Getting Crap Past the Radar: Two young boys commit abortion while inside of a giant monster. The baby is referred to as a larva, but it's clearly being terminated before it can be "born," so to speak.
- Giant Flyer: Gamera and Jiger, who seems to use some sort of steam propulsion.
- Monster Is a Mommy: Jiger, who also tries to turn Gamera into an example of M-Preg. Fortunately, this plan is thwarted.
- Nice Job Breaking It, Hero: By removing the idol from the island, the Expo workers accidentally unleash Jiger, which ties into...
- Sealed Evil in a Can: Jiger, after the idol has been removed from its spot on the island.
- Shooting Superman: Subverted. The military takes some shots at Gamera with rifles...and it works!
- Stock Footage: At the beginning of the film, we are treated to a montage of footage from the previous Gamera movies, with the exception of the first film. Also, during Jiger's attack on Osaka, footage of people in shelters is taken from Gamera vs. Barugon.
- Underdogs Never Lose: Gamera is defeated by Jiger twice before he finally wins.