Prelude to a Nightmare (悪夢へのプレリュード Akumu e no Pureryūdo) is the twenty-third episode of Ultraman Z.
STORAGE has developed the 4th Special Airborne Armor, Ultroid Zero, based on analysis of Ultraman! Yoko is chosen as its pilot, but on the day of its launch test, monsters begin to rampage all over the place! In the face of a monster attack of unprecedented scale, STORAGE unveils their most powerful robot to show off its true strength!
A month after the D4 testing on urban area, director Kuriyama made it official in GAFJ's public announcement that SAAG replaced STORAGE to manage the SAA units. Despite concern about the D4 Ray's destructive properties, Ultroid Zero was showcased to ensure both the superweapon's usage and the fact that mankind has no longer need to rely on the Ultra's help. Former members of STORAGE can only watch in disgust as Kuriyama suddenly muttered Karekareta.
Now relegated to the job of a security guard, Haruki sees the clouds above him forming Sevenger, Windom and King Joe SC as he misses the days he spent as a STORAGE officer. While having a lunch alongside Yoko, Haruki learns that Hebikura was officially discharged from GAFJ. He also discover that Yoko's tendency for arm wrestling matches came from her father as a former GAFJ officer who taught her to marry someone who could best her in a fight. Up until now, no other men were able to defeat her. Before the two parted ways, Haruki tells her that he will be on guard during Yoko's test pilot of Ultroid Zero. Yuka discovers that the five monsters under GAFJ's supervision begin showing signs of irregularity in their movements, especially since everything are related to Ultroid Zero's experimentation, but her pleas fell on deaf ears.
On the testing day at Yugiri, citizens and mass media came to record Ultroid Zero. Yoko's activation of the SAA unit triggers the simultaneous awakening of Takkong and King Guesra from the Tsuruga Bay and Demaaga from Mount Kuzuha. Haruki/Z decided to leave for Tsuruga Bay, allowing Yoko/Ultroid Zero to deal with Demaaga. Unfortunately both of them were outnumbered and overpowered, as Pagos and Gomess even came to Demaaga's aid before the sea monsters entering the fray too, all united to destroy the mechanical Ultraman. The sea monsters decided to back off after they were defeated by Delta Rise Claw, but the subterranean monster trio were decimated by the D4 Ray when Yoko used it under Kuriyama's pressure. Although the beam output was controlled, but Ultroid Zero deactivated from the backlash and Yoko fainted as well. Mai Yuki, the head developer of the SAA-4 was the only person to cheer for this.
Z quickly extracted the unconscious Yoko from the cockpit, but Hebikura appears out of nowhere to expose his true identity as Juggler, much to Haruki's shock.
- Haruki's Ultra-navi! 'Kay! Today we're showing this!
- Z Riser: Red King.
- Z: Red King! A monster who boasts amazing might!
- Haruki: Red King was the one that made me realize that monsters are living beings, too. I'll never forget it again!
- Z: That's right. Let's protect peace for everyone together, Haruki!
Ultraman Z and Ultraman Zero Voice Drama
Recruitment Examinations ② (採用試験② Saiyō Shiken ②)
After being told by Mebius about an alternate way to pass the Inter Galactic Defense Force recruitment test, Z prepares to challenge someone for his final test. It turns out to be Ultraman Zero, who is also testing to see if Z is worthy of becoming his disciple.
- Haruki Natsukawa (ナツカワ ハルキ Natsukawa Haruki): Koshu Hirano (平野 宏周 Hirano Kōshū)
- Yoko Nakashima (ナカシマ ヨウコ Nakashima Yōko): Rima Matsuda (松田リマ Matsuda Rima)
- Yuka Ohta (オオタ ユカ Ōta Yuka): Hikari Kuroki (黒木ひかり Kuroki Hikari)
- Shota Hebikura (ヘビクラ ショウタ Hebikura Shōta): Takaya Aoyagi (青柳 尊哉 Aoyagi Takaya)
- Director Kuriyama (クリヤマ長官 Kuriyama Chokan): Hisahiro Ogura (小倉 久寛 Ogura Hisahiro)
- Mai Yuki (ユウキマイ Yūki Mai): Maya Hayashi (林 摩耶 Hayashi Maya)
- Newscaster: Sakura Miyajima (宮島 咲良 Miyajima Sakura)
- Yoko's Father: Masataka Matsubara
- Reporter: Yue Mochinaga
- Ultraman Z (ウルトラマンゼット Urutoraman Zetto): Tasuku Hatanaka (畠中 祐 Hatanaka Tasuku)
- AI voice (AI 音声 AI Onsei): Katsumi Fukuhara (福原 かつみ Fukuhara Katsumi)
- Beliarok (ベリアロク Beriaroku): Yuki Ono (小野 友樹 Ono Yūki)
- Ultraman Z: Hideyoshi Iwata (岩田 栄慶 Iwata Hideyoshi)
- Ultroid Zero: Shinnosuke Ishikawa (石川 真之介 Ishikawa Shinnosuke)
- King Guesra: Yuma Eichi (永地 悠斗 Eichi Yūma)
- Takkong: Shun Takahashi (高橋 舜 Takahashi Shun)
- Demaaga: Kenji Kajikawa (梶川 賢司 Kajikawa Kenji)
- Gomess: Satoru Okabe (岡部 暁 Okabe Satoru)
- Pagos: Hiroyuki Arai (新井 宏幸 Arai Hiroyuki)