Gyokko's design takes the form of a pale white, abstracted, grotesque humanoid figure with an upper torso that has no arms and resembles that of an armless statue growing from a porcelain pot; similarly to a djinn. He has multiple infant-like hands that line his back. Gyokko's face is somewhat even more distorted. Large green mouths displace the position of where one would expect eyes, and his actual eyes are located vertically from one another on his face; One eye appearing in the constantly open bottom mouth and the other is seated at the center of his forehead. As Upper Moon Five, the Kanji for number five and Upper Moon is engraved on each one of his honey brown eyes.
Gyokko is depicted to be short tempered, shallow and arrogant, especially when it comes to things regarding to his "Art" as he seen when he was easily angered and enraged by Muichiro when he began to insult and make fun of the quality of his art and through his conversation with the pillar, constantly praised himself as "beautiful" and his work even more so, further reinforcing his arrogant and narcissistic personality, he's also shown himself to be incredibly shallow, petty and jealous, as seen when he attacked and mutilated Hotaru Haganezuka due to his jealousy of the latter focus and dedication to his work, surpassing his own zeal when working on his own art and made him want to instead make the latter lose his focus and waste time on the swordsmith due to this petty jealousy. He is also shown to be incredibly morbid as when Doma told him he placed a human head on top of his pots like a plant, Gyokko immediately saw it as more inspiration for his "Art", the extent of this morbid and violent inspiration for his "art" is shown even more when he brutally murdered several swordsmiths and used their corpses to create a "beautiful" piece by stitching their bodies together along with sticking several swords into them, this extreme sadism is shown even further when he built in the feature of them to scream when a sword is shoved deeper into his "artwork" implying that they were still alive.
Having been summoned to a gathering of the Upper Moons, Gyokko greeted Akaza, asking him how he was after ninety years and barely hiding his disappointement of the idea of his colleague's survival along this years. The potted Demon also greeted Doma, exchanging small talk about the pot he had given his fellow Upper Moon as a gift. Shortly after this, Gyokko listened as Muzan Kibutsuji informed the group that Gyutaro had died and berated them for their uselessness. The Upper Moon informed his leader that he had information that would get him closer to achieving his goals, only to have his head ripped off due to the information being unconfirmed. He was then ordered to head over with Hantengu once he corrected his mistake, leaving him bemused. The potted Demon was then approached by Doma, who asked him about the information he had and if he could tag along, and was shocked as Akaza destroyed Doma's head from behind.
At the swordsmiths' village, Gyokko devoured an unsuspecting villager and spat him right back out, stating that it wasn't edible. He then noted that destroying the swordsmiths' village would severely weaken the Demon Slayers.
When Muichiro Tokito and the two villagers come upon the shed looking for a new sword, Gyokko ambushes them from a ceramic pot. He introduces himself and asks if Muichiro would like to see his art. He then presents "L'Agonie Des Forgerons," (French for "Death of Swordsmiths") a morbid piece consisting of multiple swordsmiths' bodies stitched together with swords sticking out of them.
Once attacked by Muichiro, he retreats inside his ceramic pot and reveals he can transport himself from pot to pot at will. He explains that the pots are his pride and artwork, and becomes very upset when they are damaged. He then summons many fish from a pot and uses Fish Assassin: Thousand Needles to attack Muichiro, who lets himself be hit. Gyokko wonders what art he should make for Muichiro, but is rebuked and told he is worthless by Tokito. Upset again, he traps Muichiro with his Blood Demon Art, Water Basin of Hell, commenting that suffocation is "quite chic, quite beautiful."
While Muichiro struggles to escape the Water Basin of Hell, Gyokko advanced upon the shed. He enters and sees Hotaru Haganezuka working on the blade extracted from the training doll. Hotaru doesn't notice Gyokko's entrance behind him, enraging Gyokko at the prospect of another artist more concentrated on his craft than he. He summons a fish to attack Hotaru, breaking the sword-smith's mask but not his concentration. Hotaru's dedication to the blade incentivizes Gyokko to force him to break his concentration rather than straight-up murdering him.
Muichiro escapes from the Water Basin of Hell with help from Kotetsu, surprising Gyokko and causing him to unleash Octopus Pot Hell. Muichiro's Sea of Clouded Mist nicks Gyokko, and he ducks back into his pot, reappearing in a different pot. He argues with Muichiro about the beauty of his pots, becoming enraged after an insult to their balance, and unleashes Ten Thousand Gliding Clay Fish. After Muichiro deflects two of his attacks, Gyokko reveals his true form and becomes more serious about killing him. Gyokko's true form has the ability to turn anything he punches into fish, and has heightened speed and strength. Muichiro uses Breath of Mist, Seventh Form: Haze to decapitate Gyokko, killing him.
Abilities and Powers
As Upper Moon Five of the Twelve Demon Moons, Gyokko is a powerful Demon with several unique powers and techniques that allows him to easily outclass average demons and give him the necessary edge to overwhelm and kill the Pillars of the Demon Slayer Corps, as seen when for the majority of his Battle Against the Mist Pillar, Muichiro, he managed to easily hold the advantage over him and would have likely killed him if he had not awakened his Demon Slayer Mark.
- Enhanced Regeneration - As a Demon he possess powerful regenerative abilities that were augmented even further upon being given more of Muzan's blood. He was able to survive being decapitated by Muzan and later was able to reattach his severed head without much difficulty. He also displayed the ability to quickly heal injuries inflicted by Nichirin Blades without difficulty.
- Speed - Gyokko displayed incredible speed and reflexes as seen when he was able to easily evade and prevent himself from being cut by Muichiro Tokito despite the latter using his Breath of Mist Techniques to hinder and throw off Gyokko's senses.
- Pots: Gyokko is able to teleport into different pots to avoid attacks. Though he cannot do this if the pot is destroyed.
- Summoning: He can also summon nonsentient, fish-like demons from these jars; though it is not clear whether he makes them inside the jars, or if he summons them from different locations. These summons could be related to the demonic creatures in Muzan's base.
- Molt: In an emergency, Gyokko can molt in order to change his appearance. With his appearance changed, Gyokko gets a lot stronger. His body is covered in transparent scales that are harder than diamonds which were kneaded together inside his pot. Only three people have ever seen Gyokko in this state. Everything that he touches with his fists gets turned into sweet little fish.
- Fish Assassin: Thousand Needles!!! (Senbonbari Gyosatsu): Gyokko creates from his pots fish-like demons that spit poisonous needles.
- Octopus Pot of Hell!!! (Takotsubo Jigoku!!!): Gyokko creates from his pots giant octopus-like tentacles that he uses to destroy his surroundings.
- Water Basin Of Hell (Kekkijutsu Suigo-kubachi): Gyokko creates a vase shape-like structure made out of water that traps its opponent. After that, the enemy will be suffocated to death and aside from being very hard to cut it, this technique makes it harder for a demon slayer to escape since they can not use their Breath Styles if they cannot breathe.
- Ten Thousand Gliding Clay-fish!! (Ketsuki-jutsu Ichiman Kakkuu-nengyo): Gyokko creates from his pots fish-like demons that feed on its enemy flesh, even if the opponent cut these fishes they will spread a poisonous liquid before the Nichirin Blade can turn them into dust. The poison is also percutaneous meaning it can be absorbed through the skin.
- Deadly Scales of War: Gyokko's ultimate technique. He claims that the scales covering him make him a free existence which allows his attacks to become unpredictable.
- Gyokko's summoned fish-like Demons are reminiscent of Junji Ito's fish demons from "Gyo."