Masaru Sakamoto, head character designer for both SSSS.GRIDMAN and SSSS.DYNAZENON designed Zaiohn after listening to director Akira Amemiya, and made sure to incorporate things he disliked, such as shiitake mushrooms, boneless soft bodies, slime, and tried to make them look cute. Particularly, the mouth area is designed in reminiscence of the folds on a shiitake mushroom. Its main eyes are designed based on Leucochloridium even though it was not mentioned by the director, because Sakamoto thought Amemiya would hate it anyway. Zaiohn's inner eye is based on other Kaiju with an eyeball motif such as Gan-Q. He also designed the hands in a way that the hypothetical suit actor's arms would not fit in and instead droop down.
The way Zaiohn rubs its hands together was screenwriter Yuuichi Abe's idea, based on his fear of insects.
A trio of children come across Zaiohn in a patch of grass and observe it. Sizumu then inspected the creature himself and determined it was a failed Kaiju. Zaiohn then ran off and put paint on Gauma's face while he was sleeping, shocking him when he found out. Gauma then called the others and ordered them to look for it, even though it was seemingly harmless. Yomogi Asanaka and Yume Minami manage to find Zaiohn shortly after, and tied it with some rope. Gauma then came along with Chise Asukagawa and Koyomi Yamanaka. Gauma wanted to kill the Kaiju with a rake, but was stopped by the others saying it was harmless and didn't really deserve to die. Gauma tried his Instance Domination on the Kaiju but failed, having lost his Kaiju User powers. The others then started to imitate him, but when Yomogi's turn came he found that he was able to actually connect with the Kaiju for a moment, seeing its core. Gauma then kept Zaiohn with him in a cage for the night.
The next morning, Gauma found that Zaiohn had escaped. He called the others again but this time, Knight and the 2nd appear, with the former reprimanding him for losing the Kaiju. They search around the city, now colored all over, but find Zaiohn having grown to giant size somehow, but was not quite rampaging. Gauma and Koyomi sortied in Dynadiver and Dynastriker respectively, but Koyomi stopped Gauma from firing missiles at it to prevent collateral damage. Zaiohn climbed up a building that Yume was in, putting her in danger. Yomogi, who was with Knight at the time, unleashed Dynasoldier but in the presence of Gridknight, it transformed into the Dynamic Cannon. Worried that the Kaiju might have a heart after all, Yomogi hesitated to kill Zaiohn despite the danger it currently posed, and tried to use Instance Domination on it once more, but that caused an eye to come out of Zaiohn's mouth, seemingly looking directly at Yomogi. After an intense staredown between Yomogi and Zaiohn, Yomogi decided to fire the Dynamic Fire and completely destroy Zaiohn.
- Powers and Weapons
- Paint: Zaiohn's only ability is to paint its surroundings with random colors.