15 years later... A member of Xio, Oozora Daichi, hears a mysterious voice while in combat against a monster. "Unite..." Just as Daichi is on the verge of being obliterated by the creature, he finds himself bathed in a radiant light.
"You and I have united! With our hearts as one, we will fight this monster!" Having joined with the mysterious being of light, Ultraman, Daichi becomes Ultraman X to face threats against Earth!