Seven years have passed since Ultraman Trigger protected the world from various threats. In the present, Kanata Asumi, who is a positive young man, peacefully lives together with his grandpa. One day, while delivering ordered food, he witnessed a catastrophe: Spheres from the outer space attack Earth and Mars. Motivated by saving the precious lives of the people, he merges with Ultraman Decker and joins GUTS-Select, in order to protect what's important.