Piyon, also romanized as Pyon in some English releases, is a supporting character in Hunter × Hunter. She is a Paleograph Hunter, meaning she specializes in discovering and protecting ancient documents, and she is also a linguist, an interpreter, and a programmer. She speaks multiple languages, works as a translator, and is capable of writing her own language-analysis software. She is a member of the Zodiac Twelve, the small council of elite Hunters selected by former chairman Isaac Netero to run the Hunter Association, and her code name within the group is Rabbit. Very little is known about her personal background; details such as her age, birthplace, height, and family history are never established. She first appears during the 13th Chairman Election, which takes place after Netero's death, and she remains active when the Association begins preparing its expedition to the Dark Continent.

Her appearance deliberately reflects her zodiac animal. She is a young woman of average height with medium-length orange hair, and she wears a costume consisting of bunny ears, a miniskirt, a fluffy round tail, long arm warmers, and a collar, with a tattoo of a rabbit's head on her right shoulder blade. In personality, she is laid-back and easygoing, with a casual way of speaking, and she is the most technology-oriented member of the Zodiac Twelve, often using her cell phone or laptop even during important meetings. When her emotions are stirred, however, she becomes sharp-tongued and bluntly speaks her mind, and she dislikes being ignored, raising her voice and shouting when she feels she is not getting attention. She is also skilled at political maneuvering. Her directness is most visible in her dealings with Pariston Hill, whom she openly distrusts; she calls him a kickback prince, accuses him of exploiting hunters hired on a temporary basis, criticizes his lateness, and strongly opposes his proposal to make himself chairman without holding an election. She also shows displeasure at Ging Freecss's candidacy. Her motivations are not explored in depth, but the story presents her as ambitious enough to run for chairman herself while also genuinely concerned with fair process and honest administration of the Association.

Within the story, Piyon has a prominent role during the 13th Chairman Election. She serves as a polling witness alongside Ginta and Kanzai, helps draft the election rules at Cheadle Yorkshire's request, and, as a candidate in her own right, works to gather votes in her favor. In the first round of voting she ties with Cluck for ninth place, and after the results of the fourth round she loses her candidate status. From the eighth round onward she acts as the moderator of the assembly, guiding the proceedings, announcing results, managing the order of speeches and questions, and keeping order in a hall filled with more than six hundred Hunters. At one point she shouts at Leorio Paradinight for not paying attention, and later she has to quiet the crowd when Gon Freecss appears. The election ultimately ends when Pariston wins the final vote but immediately names Cheadle his vice-chairman and steps down; Piyon's own bid for the chairmanship does not succeed.

Her relationships with other characters are mostly professional. She works closely with the other Zodiacs, especially Cheadle, while her relationship with Pariston is defined by suspicion and blunt criticism. In terms of ability, she was strong enough to serve as Netero's sparring partner, which indicates considerable combat skill. During a brief encounter, Hisoka Morow estimates her overall ability at 77 points, a score that places her above many professional Hunters but below Kanzai, Ginta, and Illumi Zoldyck. Kanzai also considers her stronger than two veteran specialist Hunters, including Knov. Her specific nen ability is never shown to the audience; during the Succession War arc she agrees to reveal her ability to the other Zodiacs, but its nature remains undisclosed. In the Dark Continent arc, her expertise becomes central to the mission: she is assigned to the intelligence team preparing for the voyage, and she works on loading ancient-language data into her software in case the expedition makes contact with an unknown civilization. On board the Black Whale she is seen with other Zodiac members in the ship's lower levels, and Kurapika, using his dowsing chain, privately confirms that she is not one of the agents feeding information to the enemy. As a supporting character, she does not undergo a major personal transformation, but her role grows from an assertive election moderator into a trusted specialist whose linguistic and technical talents are relied upon for one of the Association's most dangerous undertakings.