A living remnant of the dinosaurs that is believed to have lived in Scotland’s Loch Ness since ancient times. Jirahs uses its enormous frills to intimidate opponents, and attacks with light blue destructive beams fired from its mouth and long tail.

After scientist Professor Nikaido discovers Jirahs in Loch Ness, he adopts the alias Professor Nakamura and brings Jirahs to Kitayama Lake to raise it in secret. Kitayama Lake’s environment is similar to Loch Ness, and over the next 15 years Jirahs grows to giant proportions. Hiding below the surface in the day, Jirahs comes out to feed at night, surfacing when Professor Nikaido’s summons it. However Jirahs is hurt when two fishermen begin spilling chemicals in the water to more easily catch fish. It rises to the surface and comes ashore, ignoring the Doctor’s commands.

Shrugging off the SSSP’s attacks from the Spider Shot, it continues to advance towards them, but is drawn into a fight when Ultraman appears. Ultraman evades its destructive beam attacks and even tears off part of its frills, prompting Jirahs to charge forward in a tackle only for Ultraman to dodge every time. A fierce battle follows until Jirahs is defeated by Ultraman’s Ultra Haze Slice.