(First Aired: September 18, 1966)
Screenplay by: Tetsuo Kinjo
Directed by: Kazuho Mitsuta
On a full moon night at quiet Lake Kitayama, an old scientist named Dr. Nakamura rows from his lakeside mansion on a boat with bucketfuls of dead fish. He calls out to a beast he calls Jirass as he pours the fish into the water. The water starts bubbling as an enormous but unseen form consumes the fish. The mad scientist smiles at his creation, speaking to Jirass like a father to a son and warning the monster to remain below the surface in daytime to keep out of human eyes. The following day, fishermen enjoy the bountiful harvests at Lake Kitayama, but the increase of fish has caught the attentions of Science Patrol, who note that Lake Kitayama’s fish populations have increased at an unnatural rate. Hayata and Ide are sent in the Jet V-TOL to drop off the S21 Submarine carrying Arashi in the lake. The submarine search turn up nothing, but Muramatsu lets the team stay at the lake as a sort of bonus vacation.
While Hayata, Ide, and Arashi relax at a hotel not too far from Lake Kitayama, a different group investigates the lake. Reporter Kubo and her photographer Hayashi of Shonen Graph are visiting Dr. Nakamura’s lakeside mansion to ask the man on his area of expertise (or perhaps more accurately, obsession) – dinosaurs. More specifically, they want his word on the Loch Ness Monster for Shonen Graph’s upcoming Nessie-themed issue, as Dr. Nakamura is dubbed "Monster Professor" by his colleagues for a reason. Inside, Dr. Nakamura says that he believes Nessie is a surviving Diplodocus. Then, he is asked about Dr. Nikaidou, who had disappeared on a Nessie hunt fifteen years ago. Nakamura says Nikaidou was a dinosaur-crazy paleontologist like him. The monster hunt had been cut short, so Nikaidou went to find Nessie by himself. That was when he disappeared, to which Nakamura adds that if he had been eaten by Nessie, it would have been the culmination of his lifelong obsession with surviving prehistoric reptiles – a trait he and Nakamura share. Nakamura then refuses to answer any more questions about Nikaidou or Nessie, demanding Kubo and Hayashi to leave.
Kubo and Hayashi return to their hotel, which is the one Hayata, Arashi, and Ide are staying at. Kubo and Ide meet up and decide to go on a night fishing date in short order. At Lake Kitayama, Kubo and Ide see a great amount of rumbling foam clear made by something massive under the lake’s surface. The two also spot Dr. Nakamura at the lake and decide to follow him. During the trail, Ide stops to take a Science Patrol badge off his shoes and place it on a tree as a marker. Soon, Kubo and Ide find a secret passageway into the scientist’s lab, where Dr. Nakamura has been waiting for them. Knowing they have seen his secret, Nakamura holds Ide and Kubo at gunpoint. Then, Hayata and Arashi contact Ide and ask him when he will return. Nakamura responds by tearing off Ide’s communicator badge and smashing it before explaining that his Jirass is the result of fifteen long years of top-secret research and experimentation, and that all witnesses of his creature must be kept silent by any means.
The next day, Muramatsu and Fuji head out to meet with Hayata, Arashi, and Hayashi so they can find Ide and Kubo. At Lake Kitayama, some of the fishermen from yesterday have returned to catch every last fish in the water by poisoning the lake. Dead fish float to the surface in the hundreds, but the poisons have disturbed Jirass, who now reveals itself to the light of day in its whole form, which is quite literally a frilled version of Godzilla. Science Patrol see Jirass rising out of the lake and take ground action, while Dr. Nakamura demands Science Patrol to stop attacking his creation. Muramatsu tells him that he should being using his knowledge in dinosaurs for more practical ideas like Dr. Nikaidou did. Dr. Nakamura laughs at the notion and decides to reveal the truth. He reveals his face to be a mask by removing it. Underneath the disguise is Dr. Nikaidou, who had disappeared all those years ago in order to work on creating Jirass! Dr. Nikaidou runs off from the shocked team, commanding his monster to destroy everything in sight, though he is brutally injured by his berserk monster. Back with Ide, he has finally fixed his communicator. He contacts his teammates, giving them his location and explaining that he left his shoe badge as a path marker. The team finds it quickly and rescue Ide and Kubo. Meanwhile, Hayata goes on a different path to become Ultraman!
Ultraman flies towards Jirass, who is busy trying to smash Nikaidou’s mansion with Science Patrol inside. Jirass turns its attention to Ultraman, while Science Patrol escape to safety. Jirass and Ultraman begin their brawl with showing off their strength by tossing rocks into the air and using their respective electric breath and Specium Ray to blow them up midair. The real battle begins quickly afterwards. In the fight, Ultraman tears of Jirass’ frill (turning the fight into the closest thing ever to an official Ultraman vs. Godzilla) and uses it to mock the monster like a matador with a bull. He soon drops the act and returns to standard fare, eventually killing Jirass with a vicious strike to the chest. Looking over Jirass’ corpse, Ultraman takes the monster’s torn frill and places it on the neck like a bouquet of flowers on a gravestone. He then takes a moment of silence before leaving. Perhaps, Ultraman saw some sympathy for Jirass or viewed the monster as a Worthy Opponent. The gravely wounded Dr. Nikaidou crawls to Jirass’ corpse, sobbing at the death of the living dinosaur he had worked so hard on before dying himself. Science Patrol takes pity on the lunatic and his monster, commenting that his obsession over prehistoric survivors had become his end.
Tropes:
- Alas, Poor Villain: Science Patrol takes pity on Dr. Nikaidou, commenting that his obsession with dinosaurs was what led him to his end.
- Busman's Holiday: Muramatsu lets Hayata, Ide and Arashi take a bonus vacation at Lake Kitayama, only for them to uncover Dr. Nakamura and his pet dinosaur while staying there.
- Cool Car: Kubo and Hayashi drive a badass-looking car with the front modified to look like an animal's face when going to interview Dr. Nakamura.
- Creepy Crows: Dr. Nakamura keeps a crow among the many creatures he has in his lab, with its cries punctuating the eeriness of his laboratory.
- Latex Perfection: This is how Dr. Nikaidou disguises himself as Dr. Nakamura to conduct his research in secret.
- Mood Whiplash: After a rather comical battle between Ultraman and Jirass, the episode suddenly turns somber again when Ultraman mourns Jirass' death, and Science Patrol comments on the tragedy of Dr. Nikaidou's life.
- Non-Malicious Monster: Jirass is perfectly content to just dwell in the lake and only come out at night, but fishermen poisoning the water caused it to rampage. Ultraman even puts his frill back on his corpse as a sign of respect before leaving.
- Not Zilla: Jirass is quite literally Godzilla with a frill, and even has a similar-sounding roar and Breath Weapon. As if the producers realised they weren't fooling anybody, Ultraman tears the frill off during their battle, removing any visual differences between Jirass and the King of Monsters.
