Her shoe looks like hiking shoes, with a orange touch with black laces. ONE right leg has a long black sock with the other side having a under-knee black sock with 3 white lines going across. On her left leg, there is a tattoo, with the same being on both sides, being black and orange. ONE has what it looks like being a skirt like shorts with a messy white belt. She has a 'sporty' look with a white top under a orange zipper-up tank top. Like IA's two braids on her side, ONE has a matching braid for the bottom. To match with her older sister, IA, ONE carries the 'sexy punk look.' Her hair on the front is rather short with a orange tint on the ends, with some hair spreading out on the top. Their relationship to ONE (and IA) is unknown, however they were announced to be “ARIA” members. ĭuring the IA 9th & ONE 6th Anniversary ‒Super LIVESHOW- on January 27th, 2021, three additional characters were unveiled, one of whom bares the name 'H' on their nametag and the other two being an anthropomorphic lion and a reindeer-like creature. It was revealed that he learned how to transform into a human form from Chōrō. He acts as a singing teacher and voice trainer for IA and ONE.

The last member introduced in the series is a large white phoenix named “フェニックス”(also known as “Phoenix” or simply known as “Nix” ).She is described as being stern and is able to move very quick. Cheet acts as IA and ONE’s dance teacher. The third member revealed was a purple, bipedal cheetah named “チート” (also known as “Cheet”).He was described to have taught IA and ONE all that they know. He is very knowledgeable about ARIA and is connected to everything on the planet. Chourou is described to be one of the oldest spirits on Planet ARIA and acts as a “grandfather” figure to IA and ONE. The second member revealed is a large elder tree named “Chourou” (“長老”, meaning elder) or 'Choro no ki”, (長老抜き,meaning the eldest tree.).She is described as being a very sweet cat that watches over IA & ONE. She acts as a mother and has been with IA & ONE all of their lives and came to Earth with ONE. A gray, multicolored cat named “チコー” (also known as “Neko-san” or simply as “cat”) is one of the spirits that exists on ARIA.Four inhabitants of the planet were introduced and their relations to IA and ONE were revealed: Planet ARIA is described as a world similar to Earth with various life forms that resonate and co-exist together, several of whom raised IA & ONE.

In a series of YouTube videos dubbed ARIA STATION, IA and ONE introduced their home-world known as Planet ARIA. ONE has little background, however she and IA were given some background information for the ARIA - IA Musical & Live Show – performances. ONE is the second installment in the '- ARIA ON THE PLANETES -' project.

Ia and one vocaloid