Alternate Dimension Being Yapool started invading Earth with an entourage of "Terrible-Monsters" that were more powerful than ordinary monsters. The Terrestrial Defense Force was annihilated by Terrible-Monster Verokron. Two youngsters, Seiji Hokuto and Yuko Minami, lost their lives trying to save people from the attack of Verokron. Ultraman Ace, who was sent from Nebula M78 Land of Light to stop Alternate Dimension Being Yapool's malicious ambition, vested his life and power in Seiji Hokuto and Yuko Minami. Hokuto and Yuko, who received a new life, joined the Terrible-Monster Attacking Crew (TAC) that was organized in place of the Terrestrial Defense Force. When the Ultra Rings, the proof of membership of the Galactic Federation, glitter, after performing Ultra Touch, Hokuto and Yuko unite and transform into Ultraman Ace.