Amia is the younger sister of Ultraman Joneus. She's an Ultra-being like her older brother. Her only power is her Amiassher energy beam (which is relatively weak). Despite having her transformed form shown, she does not bear a proper Star Symbol and can not become giant size. Even her social and time restraints as a simple worker, she sometimes goes down to Earth against regulations.

Amia was the younger sister of the Ultra-being known as Joneus, when her brother fell on Earth his human host was brought to U40 to revive both of them. There she acted as his friend as she helped the young man recover his memories and explained the nature and origins of the conflict between Ultras and monsters. Sometimes after the battle between the people of U40 and the Hellar fleet, Amia snuck aboard Hellar's capital ship to attempt a rescue of the Great Sage of U40. Unfortunately she was captured and watched with the Science Guard Party as he was digitized and stored on a card. When Choichiro transformed into her brother, rescuing everyone, Amia took it upon herself to revive the Sage and teleport away with him.