When the Aegis Shines (イージス 光る時 Ījisu hikaru toki) is the fifth episode of Ultraman X. This episode not only feature the debut of Ultraman X's Ultraman Zero Armor, but also the return of Ultraman Zero after his appearance in the last movie.
While Xio members performing experiments to turn monsters into Spark Dolls, Black King appears and attacks the test site while Alien Nackle Bandero takes this opportunity to steal the Spark Dolls. Ultraman Zero appears and battles Black King but realizes that the plan failed, Nackle escapes with Black King and brings Rui as a hostage in another dimension. To save Rui, X and Zero join forces.
At the Operation Base X, Rui takes a test run on her cotton candy gun while Gourman teaches Daichi of the super-dimensional theory. Soon, the lab team tries to enact an experiment to turn monsters into Spark Dolls based on Ultraman X's Xanadium Beam. While on a journey to the test site, a black monster attacks the convoy. While Xio members attack the monster, it seemed that it tries to target Xio Aramis for bringing the Spark Dolls.
Daichi runs away from Aramis, unknowingly spotted by Gourman and hides to transform into Ultraman X. While X fights the monster, a poncho-wearing alien named Alien Nackle Bandero approaches and defeats Wataru, trying to steal the Spark Dolls but stops when his monster, Black King, is in a pinch. He grows up and assist it in fighting X, overpowering him but once he tried to take the Spark Dolls, a giant appears from the wormhole, having hunting Bandero in various dimensions. Gourman knows him as the "infamous" Ultraman Zero. Zero attacks Black King and manages to torn off his horn. But Bandero nonetheless goes to another dimension by picking the Aramis, with Rui inside and leaves with Black King. Zero wants to kill them but X warns that a hostage is inside, angering him and goes to the same dimension Nackle escape to.
Rui finds himself in an alien world, where Black King receives a new cybernetic horn while Bandero contact his client. Spotting the Ultlaser, she grabs it and tries to attack but loses control. Despite that, it gives her time to run with the Spark Dolls in Aramis. Rui's communication though manages to reach Earth and Xio base, but the source of the broadcast is Area T-9C, which turns out to be the "resting place" for his parents in the Ultra Flare. As Daichi talks to X, Zero intrudes the X Devizer and wants to meet them at the space. Zero reveals to X of his background and reveals Rui's location on Planet Guillermo but insists to go himself. Returning to base, Daichi sees everyone trying to create an Ultimate Zero card that allows the user to go on any dimensions.
At Planet Guillermo, Bandero finds Rui and offer her a place by making him weapons to sell but she refuses and runs away. Bandero turns huge but Ultraman Zero enters and attacks him, with Black King Drill Custom enters to join his master. As the Ultimate Zero card completed, Gourman silently delivers it to Daichi as he transforms and use the card to assume Ultraman Zero Armor to go to Planet Guillermo. As he arrives, X takes on Black King Drill Custom, using Ultimate Zero, Gomora and Eleking Armor while Zero attack Bandero with Strong-Corona and Luna-Miracle forms before finishing him off with the Zero Twin Shoot while X finishes off Black King Drill Custom with his Xanadium Beam
As the battle ended, Rui picks Black King's Spark Doll and takes a picture with Zero, having infatuated to him, with X joining them in the picture. Zero bids farewell and wishes to meet again sometime later while X returns to Earth with Rui.
Daichi's Monster Lab
- Daichi: Daichi's Monster Lab! This time, we met this monster.
- X Devizer: Analyzing, Eleking!
- Daichi: Space Monster Eleking, Rui's favourite monster. She likes him so much and wants to go on a date with it.
- X: And today's Cyber Card is Ultraman Zero. Zero is the Ultraman the Space Garrison knows they can count on. When we wear this armor, it lets us travel in between dimensions.
- Daichi and X: Well, see you next time!
- Daichi Ozora (大空大地 Ōzora Daichi): Kensuke Takahashi (高橋健介 Takahashi Kensuke)
- Asuna Yamase (山瀬アスナ Yamase Asuna): Akane Sakanoue (坂ノ上茜 Sakanōe Akane)
- Wataru Kazama (風間ワタル Kazama Wataru): Yoshihiko Hosoda (細田よしひこ Hosoda Yoshihiko)
- Hayato Kijima (貴島ハヤト Kijima Hayato): Ukyou Matsumoto (松本享恭 Matsumoto Ukyou)
- Mamoru Mikazuki (三日月マモル Mikazuki Mamoru): Hayato Harada (原田隼人 Harada Hayato)
- Rui Takada (高田ルイ Takada Rui): Haruka Momokawa (百川晴香 Momokawa Haruka)
- Takeru Yamagishi (山岸タケル Yamagishi Takeru): TAKERU
- Chiaki Matsudo (松戸チアキ Matsudo Chiaki): Chiaki Seshimo (瀬下千晶 Seshimo Chiaki)
- Sayuri Tachibana (橘さゆり Tachibana Sayuri): Sarara Tsukifune (月船さらら Tsukifune Sarara)
- Shotaro Kamiki (神木正太郎 Kamiki Shōtarō): Yuu Kamio (神尾 佑 Kamio Yū)
- Ultraman X (ウルトラマンエックス Urutoraman Ekkusu Voice): Yuichi Nakamura (中村悠一 Nakamura Yūichi)
- Ultraman X (ウルトラマンエックス Urutoraman Ekkusu Suit Actor): Sakaekei Iwata (岩田栄慶 Iwata Eikei)
- Alien Fanton Gourman (ファントン星人グルマン Fanton Seijin Gourman Voice): Yasunori Matsumoto (松本保典 Matsumoto Yasunori)
- Alien Fanton Gourman (ファントン星人グルマン Fanton Seijin Gourman Suit Actor): Hiroyuki Fukushima (福島弘之 Fukushima Hiroyuki)
- Ultraman Zero (ウルトラマンゼロ Urutoraman Zero Voice): Mamoru Miyano (宮野真守 Miyano Mamoru)
- Ultraman Zero (ウルトラマンゼロ Urutoraman Zero Suit Actors):
- Sakaekei Iwata (岩田栄慶 Iwata Eikei)
- Akira Okabe (岡部 暁 Okabe Akira)
- Black King / Black King Drill Custom (ブラックキング / ブラックキングドリルカスタム Burakku Kingu / Burakku Kingu Doriru Kasutamu Suit Actor): Kazunori Yokoo (横尾和則 Yokoo Kazunori)
- Alien Nackle Bandero (ナックル星人バンデロ Nakkuru Seijin Bandero Voice): Tetsuo Kishi (岸 哲生 Kiski Tetsuo)
- Alien Nackle Bandero (ナックル星人バンデロ Nakkuru Seijin Bandero Suit Actor): Keita Rikimaru (力丸佳大 Rikimaru Yoshihiro)
- Ultraman X
- Ultraman Zero Armor
- Gomora Armor
- Eleking Armor
- Ultraman Zero
- Ultimate Zero
- Strong-Corona Zero
- Luna-Miracle Zero
- Zero showing up to save X is most likely a reference to how Ultraseven and Ultraman saved Ultraman Jack from the first Alien Nackle and Black King.
- The planet that Bandero hides away on is named Guillermo, after director Guillermo del Toro, who is the director of the Paciffic Rim and Hell Boy movies.
- At the end of episode 14 of Ultraman X, director Koichi Sakamoto revealed that Bandero's mysterious customer was in fact Alien Markind. Makindo appeared in said episode where sell Mecha Gomora's Spark Doll to Gina Spectre and ultimately shot down by Alien Shaplay in refusal to pay for his service.