Ultraman X is the main hero of his series. Originally, he was an Ultra Warrior that chased his opponent, Greeza, to the solar system and banished it towards the sun, but doing so had triggered the Ultra Flare and cost him his physical body, permanently trapping him in the digitized state that he used for interstellar traveling. In the present day, he bonded with a Xio member Daichi Oozora and inhabited the young man's X Devizer in order to lend his strength in fighting against monster threats with his physical form.

Daichi places his hand on top of the X Devizer, manifesting Ultraman X's Spark Doll and scans it. Daichi than raises the item in the air and shouts "X!".

X can transform himself into a mass of computer data for easy transportation in space. This form allows him to inhabit technologies such as Daichi's Xio Devizer, turning it into the X Devizer. However, as a result of the Ultra Flare, he is permanently trapped in the digitized state, and thus only be able to return to his physical form when transformed by Daichi, but was returned to his physical form after his fight with Zaigorg.