Subtitle: Space-Time Monster (時空怪獣 Jikū Kaijū)
Dairyuhai was the older sister of the younger Otohime. When Urashima Taro washed ashore in the present time and broke his promise with older Otohime, by opening the shell-shaped tamatebako, she died in that moment. Years later the younger Otohime arrived on shore after and pursued him. When Taro, now an old man as a result of breaking his promise, returned to the beach and met the younger Otohime, she berated for what he had done and as a result of that, her sister died. She threw the tamatebako into the sea and from there Dairyuhkai emerged, much to Taro's shock.
Before anything could be done she was attacked by the Ultra Guard, and after defeating them was stopped by Ultraseven who attempted to held her off. Seven then threw his Eye Slugger at Dairyuhkai but the monster stopped it by letting it pierce her hand and threw the blade away. During the battle, Dairyuhkai questioned why Seven chose to protect humans that tended to break promises. Taro later showed up and offered up a moonflower, showing that he had kept his promise. Dairyuhkai she absorbed him and relented disappearing in a golden light (tachyon particles).
- Suit Actor: Fujimoto Kotaro
- Dairyuhkai is one of the few monsters to fight an Ultra and not be defeated nor defeat said Ultra since their fight was not completed.
- Despite being listed as a Kaiju, Dairyuhkai is actually clearly sentient, given her motivations and the fact she spoke to Seven.
- Her roar is composed of a monster's roar and a woman's scream.
- Dairyuhkai and her sister are not the first instance of the Urashima Taro legend being used in the Ultra Series. A prior, different, Otohime appeared in Ultra Q.
- Height: 61 m
- Weight: 50,000 t
- Origin: Pacific Ocean
- Powers and Weapons
- Flight: Dairyuhkai can fly for short periods of time or levitate, such as after she was summoned via a water tornado from the sea.
- Energy Bullets: Daiyruhkai can fire several missile-like blasts from her mouth at once.
- Mist Breath: When needed, Daiyruhkai can emit a steady stream of blinding mist from her mouth.
- Telepathy: Dairyuhkai can talk to others telepathically.
- Endurance: Dairyuhkai was able to stop the Eye Slugger by allow it to pierce her hand.