A solar flare has awakened Spark Dolls from the depths of the earth and the ocean! Fifteen years later, Daichi Ozora transforms into Ultraman X to battle threats from both aliens and monsters. He is also a member of Xio, a team created to battle the monstrous threats.

When realty TV host Carlos Kurozaki breaks into a mysterious underground pyramid for a television event, he removes a special gem. . . and unwittingly releases a diabolical monster called Zaigorg! The evil creature wants Kurozaki's gem, so it spawns an army of giant kaijus to get it! It's up to the famous superheroes Ultraman X, Ultraman Tiga, and the one and only original Ultraman to stop the worldwide monster war!