Jirahs was a mutated frill-lizard Kaiju created by a mad scientist who aspired to create a legend-worthy beast. It was killed in a duel with Ultraman.

A monster created by Professor Nikaido, Jirahs was being raised in Lake Kitayama. When reports of an abundance of fish suddenly disappearing in the lake came in, the SSSP was called in to investigate. When they didn't find any clues, the captain let them go on a vacation nearby at a nice hotel until they could be picked up. When Ide went fishing with a female reporter who had interviewed the scientist, they saw the scientist out on the lake about to feed Jirahs. They then went to his house to investigate, but were beaten there by the scientist himself. When he found them in there, he took them hostage since they saw him earlier.