Ultra Brothers, Eternal Vows (ウルトラ兄弟永延の誓い Urutora Kyoudai Eien no Chikai) is the 34th episode of Ultraman Leo. It features Gen Ohtori/Ultrman Leo teaming-up with Ultraman Jack, featuring the return of Jiro Dan as Ultraman Jack's human host, Hideki Go.
Because Dan can't transform into Seven after the battle with the Giras Brothers, Ultraman Jack flies to Earth to deliver a Monster Capsule and get his Ultra Eye fixed, but along the way he gets involved in a battle with Ashuran. He loses, and his human host Hideki Go's mouth was sealed by the Monsters during the battle. He crash lands on Earth where Gen finds him, but the monster capsule was left behind.
- Ultraman Leo Volume 9 features episodes 33-36
- Complete DVD-Box features all episodes
- This episode was later featured in New Ultraman Retsuden episode 150 "Leo, Jack Coalition! Eternal Vows of the Ultra Brothers."