Taking place several years after the events of Ultraman Trigger: New Generation Tiga, in a time when the threat of monster attacks faded, and the Earth seems once again at peace. Humanity turns its eyes to the stars and heads to space, while its monster attack countermeasures continue to shrink.
20-year-old Kanata Asumi (played by Hiroki Matsumoto) is living a peaceful life and is working at his father’s rice cracker store. Cheerful and a little goofy, this kind-hearted young man is close to their neighbors and regular customers, and cares for others. He never ignores someone in need, and sometimes goes overboard, throwing his heart and soul into whatever task is before him. But his peaceful life changed because of the Sphere attack. Destruction spreads before his eyes and a giant monster appears. With no heed for his own safety, Kanata jumps in front of the enemy, and transforms into Ultraman Decker!
Having discovered the light of Decker within himself, Kanata pledges to protect humanity and joins the expert team GUTS-Select, now newly reformed by the Terrestrial Peaceable Union (TPU) as an Anti-Sphere squad. As its newest member, Kanata and his young unseasoned team stand against these great enemies together.