Welcome to Aizen Tech (アイゼンテックへようこそ Aizen Tekku He Yōkoso) is the third episode of Ultraman R/B.
The three siblings visit the passionate Makoto Aizen, president of Aizen Tech, a company located in Ayaka City and are enchanted by their displays of cutting-edge technology. It’s then revealed that the mother of the three siblings was once doing “specific research” for AizenTech. During their visit, a giant monster with the ability to turn items into stone attacks.
After discovering their mother's notebook, Katsumi and Isami question their dad on the crystals drawn on the book. Their dad didn't know much so the two brothers along with their sister visit Makoto Aizen, who worked with their mother, for answers.
Upon arrival, the three siblings admired Aizen Tech's headquarters in awe as Makoto flew in on his jetpack. The CEO greeted the visitors, but was suddenly hit on the head by a petrified bird, and was momentarily knocked out. Makoto got up and lead the three visitors to some of his workshops and showed them the gadgets he is currently working on. While Asahi ran off to explore the building, the two brothers followed Makoto into his office and asked him about the crystals. Makoto then told them a story about a meteor hitting Earth and revealing three giants. The giants then fought, with the two brothers being defeated.
Just as the story was finished, a portal opened above Ayaka City and from it appeared Gargorgon. The monster headed for the Aizen Tech headquarters and everyone in the building had to evacuate. Amid the chaos, the two brothers left the building and transformed into Ultraman Rosso and Blu. The two brothers were evenly matched against the monster, until it shot its Petrification Ray at a building, that reflects off and petrifies Blu. The monster continued to strangle Rosso with its tails. At that moment, Katsumi realised that Rosso's horns were glowing and he summoned the R／B Slugger Rosso and slashed Gargorgon's eye, reverting Blu back to normal. Blu summoned his R／B Slugger Blu and the two brothers continued fighting Gargorgon.
Katsumi thought up a plan and told Isami to switch crystals. After assuming his Aqua form, Rosso used the Aqua Mirror Wall to reflect Gargorgon's Petrification Ray back at its feet, causing the monster's own legs to turn into stone and become immobile. Blu slashed her eye with the R／B Slugger Blu and both brothers used the Cross Slugger attack to destroy the beast. After the battle, Makoto is seen placing the Gargorgon Crystal into the R／B Crystal Collection Case.
That evening, the three siblings return to their family's clothing shop and the two brothers begin concluding that the recent kaiju attacks should be coming from Mount Ayaka. They were interupted by their father and the two comment on their father's new shirt. Makoto is seen in the outskirts of the city following a man, who bears a strong resemblance to a previous character, and awkwardly greets him.
- Katsumi & Isami: R/B Crystal Navi!
- Isami: We are going to be studying R/B Crystals now Katsumi!
- Katsumi: Yeah. Today's crystal...is this!
- R/B Gyro: Grigio Bone!
- Isami: The Flame Bone Beast, Grigio Bone. Height: 60 meters. Weight: 62,000 tons. It is the legendary creature of Ayaka. It can breathe fire from its mouth, making it quite fearsome.
- Katsumi & Isami: Be sure to watch next time!
- Katsumi Minato (湊カツミ Minato Katsumi): Yuya Hirata (平田 雄也 Hirata Yuya)
- Isami Minato (湊イサミ Minato Isami): Ryosuke Koike (小池 亮介 Koike Ryōsuke)
- Asahi Minato (湊アサヒ Minato Asahi): Arisa Sonohara (其原 有沙 Sonohara Arisa)
- Ushio Minato (湊ウシオ Minato Ushio): Ginnojo Yamazaki (山崎 銀之丞 Yamazaki Ginnojō)
- Makoto Aizen (愛染マコト Aizen Makoto): Motoki Fukami (深水 元基 Fukami Motoki)
- Ultraman Rosso: Hideyoshi Iwata
- Ultraman Blu: Akira Okabe