Giant Ant Terrible-Monster vs. Ultra Brothers (大蟻対ウルトラ兄弟 Dai Ari tai Urutora Kyoudai) is the fifth episode of Ultraman Ace. It features Ultraman Ace teaming up with Zoffy. This is also the first time Zoffy, the leader of the Ultra Brothers is seen fighting villains.
Two women go missing, with witnesses testifying that they vanished underground. The only common link between the incidents was that both women had type O blood. TAC closes the case, but when Yuko and Seiji are out shopping, Yuko herself is targeted. Seiji manages to free her, and the two catch a glimpse of the terrible-monster, Aribunta.
- Ultraman Ace Volume 2 features episodes 5-8.
- This episode was later featured in episode 43 of Ultraman Retsuden, "Bonds of Brothers! Ace and Zoffy!!".