Ultras have the power to merge with humans. These chosen individuals are then able to transform into their Ultra counterpart, generally through the use of a special item. This is required due to the fact that Ultras in many continuities cannot survive long in Earth's atmosphere.
However this is not the only option open to the Ultras, like many Alien races in the series they can take on human forms, their method of transformation back into their true forms is generally the same as Human Hosts but there are some instances that brings that into question. In the Ultraman Story 0 Manga, all Ultras are born with their own human forms.
Related Post :
Source : ultra-wikia
