- Voiced by: Erino Hazuki (Japanese), Veronica Taylor (English)
The main character. An immigrant from Japan, Manhome who comes to Aqua to become an undine. Normally shown as a very cheerful person. Has a strange tendency to draw supernatural phenomena to her. Her Prima alias is "Aquamarine".
- She frequently pronounces "hai!" as "hahi!".
- She also tends to go "Ehhhh?" a lot, especially in response to Aika's own admonishing Catchphrase. Aika immediately knows something is wrong when Akira doesn't respond with that.
- In one episode/chapter, Aika claims Akari tends to get distracted and say "Ah, suteki!" which means "oh, it's wonderful," or more contextually, "Ooh, that's neat!" but this isn't really shown in practice, though.
- Cloud Cuckoo Lander
- Does Not Like Shoes: Even though she has galoshes, Akari prefers to go barefoot when she's wading through the waterlogged streets, mostly because she enjoys the cold sensation of the water and the stone paving under her feet. Should one galosh slip off in the water, she's more inclined to pull the other one off and leave them off.
- Earthy Barefoot Character: She loves going barefoot and interacting with the ground. She even got Akatsuki to take his shoes off and join her on a barefooted outing on Aqua Alta, which is simply adorable.
- Embarrassing Nickname: Akatsuki likes to call her "Pigtails" for her side locks, which she very much doesn't like (especially when he pulls on them). In the genderbending chapter this instead gets turned into "Sideburns".
- Friend to All Living Things: Not only does she befriend nearly every human she meets, but several animals and even a snow bug as well. She even feels sorry for some chocolate candies that won't get eaten because they got dropped onto the ground! Cranked up to eleven, even her gondola (in the form of an elderly man) put an umbrella over her, and if you believe her idea of who Cait Sith is, the entire spirit world of Aqua looks after her. In short, friend to all living things, and many NON-living things to boot.
- Genki Girl
- Girlish Pigtails: Really more of sidekicks, but everyone treats them like pigtails anyway and her Embarrassing Nickname refers to them as such.
- I Knew It!: In-Universe, her exclamation when she confirms that Cait Sith is the conductor on the Galaxy Express railway.
- Love Freak: Probably everyone's trait, but it's especially apparent with Akari.
- Penpals: Every chapter, Akari writes to a secret penpal about her life's events. It turns out her penpal is Ai in the anime, but it's left ambiguous whether it was a specific person or a public blog in the manga.
- Rapunzel Hair: Her "sideburns" get so long by the epilogue that she's able to loop them back around into a ponytail! How she doesn't catch her oar in those loops is anyone's guess.
- Romantic Two-Girl Friendship: Her relationship with Alicia certainly has elements of this, which culminates in the Arietta OVA.
- Rose-Haired Sweetie: The poster girl of the trope. Her pink hair matches perfectly with her cheerful, sweet and naive personality.
- She Is All Grown Up: In the anime she's the only one out of her and her two friends that's shown after reaching adulthood. In the manga she's the last one to be shown.
- Ship Tease: With Akatsuki, but also with Alicia, so much that Alicia's unexpected marriage outraged quite a few yuri fans.
- Tearful Smile: When Alicia "disappeared" after she told Akari she planned to retire.
- Weirdness Magnet: During her time on Aqua she attracts quite a few supernatural entities by either being obliviously nice or just happening to run into them. Not only does she run into the Cats on a regular basis, she's also seen ghosts, Aquan life, and even Youkai.
- Wide-Eyed Idealist
- You Gotta Have Blue Hair: Her hair is pink.
One of the three Water Fairies, Akari's tutor. Current manager of ARIA Company. She's known by the title "Snow White", and is currently the most popular Undine in the city.
- But Now I Must Go: After Akari becomes a Prima, she suddenly reveals that she'll leave Aria Company. She had promised the Gondola Association she would accept a job with them after training an Undine capable of inheriting the Aria company.
- Catchphrase: "Ara ara" ("well well/My my"), usually followed by a giggle, emphasizing her easy-going nature. They note she'd more likely say that than scold someone. They're right.
- Improbable Age: She loves up to her reputation as a Living Legend by becoming the former youngest Prima undine at 15. For reference, that was how old Akari was when she first started; it was reported that Alicia rose up the ranks in only her first year of training.
- Last Minute Hookup: Gets married in the last chapter/episode with little/no foreshadowing.
- Onee-sama: So very much.
- Passing the Torch: After constant asks for her to become a manager and representative in the Gondola Association, Alicia only agreed to do it if she could find and train a Prima fit to run Aria in her stead. Akari ended up being that girl.
- Quitting to Get Married: Subverted in the end. Akari's promotion to Prima, along with her fiancee setting up for marriage and the Gondola Association wanting her in a rep job, puts Alicia in quite a tight bind. After giving it much thought, she puts an end to her long and successful career as an undine...but she still has the rep job at current, so she's still at least in the field she knows best.
- Rapunzel Hair
- Romantic Two-Girl Friendship: With Akari.
- Ship Tease: With Akari, most prominently in the Arietta OVA.
- Shipper on Deck: She quite likes the idea of Akatsuki/Akari, often trying to get the former to do things for the latter and assuming that he actually has a crush on the girl.
- Stealth Hi/Bye: Does this a from time to time, though it usually happens in the later chapters rather than the earlier ones.
- Troll: As expected of this show, it is played very lightly and not malicious at all, but she has her moments.
- Voiced by: Yoshiko Matsuo (Japanese), Karen Smith (English)
Better known as Grandma. Legendary Undine and the founder of ARIA Company. Originally she's from Himeya Company, but break off after meeting with President Aria. Currently lives in countryside.
- Alliterative Name: Akino Ametsuchi.
- I Was Quite a Looker: She aged very badly, to say the least.
- Miniature Senior Citizens: Shrunk considerably between her working as an undine and now.
Originally an anime-only character, Ai is Akari's customer in the first episode of the anime (in place of an old man in the equivalent manga story), and serves as the character that Akari corresponds with (in place of her unknown readers in the manga). Gets Canon Immigrant treatment in the last chapter of the manga.
- Alliterative Name: Aino Ai
- Canon Immigrant
- Cheerful Child
- Hair Decorations: A big, red ribbon.
- Last Episode, New Character: In the manga.
- She Is All Grown Up: While she doesn't appear to physically grow during the 6 earth years that the series covers, that changes in the epilogue and the Avvenire OVA's.
- Weirdness Magnet: Appears to be following in Akari's footsteps of attracting the supernatural to her, lampshaded by her companions. This is also illustrated in that she is the only one aside from Akari to actually see Cait Sith at Carnivale (anime only).
- Voiced by: Risa Hayamizu
Grandma's apprentice before Alicia. Left the company after Alicia became Prima. Currently has a family.
President Aria Pokoteng
- Voiced by: Chinami Nishimura (Japanese), Tara Tisch-Wallace (English)
ARIA Company's president. A Martian cat that Akino met, and with whom she founded ARIA Company.
- Cat Smile
- Hopeless Suitor: He's rather sweet on Hime, but she won't indulge in his affections.
- The Load: Even his focus episode is based around how much he gets in the way.
- Non-Human Sidekick: Of all of the cat companions, Aria is really the only one that is consistently shown accompanying Akari during her focus stories.
- Precocious Crush: The subject of Maa-kun's, as it turns out. He doesn't know about it mainly because Maa likes to bite his tummy and bother him.
- Really 700 Years Old: Stays with the company for 20 years and he doesn't look any different at all.
- Ridiculously Cute Critter: He's got the big eyes, cute noises, cuddly physique and sweet attitude to qualify for this.
- Small, Annoying Creature: At least to Hime, he is treated like this, but mainly in the anime continuity.
Aika S. Granzchesta
Daughter of the owner of Himeya and its heir, and Akari's first friend on Aqua. Has a crush on Alicia and later Al.
Her Prima alias is "Rozen Maiden".
- Girlish Pigtails: For the first half of the series.
- Hair Decorations: A cross shaped hair ornament that she wears on her right bangs. Rather, she starts to wear it more often after she cuts her hair.
- Huge Girl, Tiny Guy: Has this dynamic with Al the Gnome. Naturally, the reverse is true in the genderbend chapter.
- Important Haircut: She used to have long hair, as she wanted to be like Alicia. However, after she accidentally got it burned at a cookout, she had to cut it short. At the same time she realised that it was better if she was her own person, and cuts it even shorter to signify the attitude change. However, she still looks up to Alicia as a role model.
- Jerk with a Heart of Gold: Though a very light version.
- Mad Libs Catch Phrase: She often says something like "__________ is/are not allowed!". Most commonly, "Embarrassing remarks are not allowed!", or in the original Japanese, "Hazukashii serifu kinshi!", often several times an episode.
- Meaningful Name: Grantchester is a village upriver of Cambridge, England, and a popular destination for summer punting trips.
- Mood-Swinger: Aika can swing between energetic, down-to-earth, lovestruck and crybaby pretty convincingly.
- Ojou: It's easy to forget, but Aika is Himeya's young heiress and has the attitude to match. She's rather humble about it, all things considered.
- Something About a Rose: Like Akira, she also has a rose motif. Her company's colors are a deep rose red, she inspired Akira with a metaphor involving rose petals, and her Prima name, like Akira, is based on roses.
- Stalker with a Crush: In the beginning of the series, she exhibits this toward Alicia.
- Tsundere: A type B. She's fussy and tries to play up a mature air, but when she's touched or wants to be more affectionate she's rather shy about it or tells off people for saying mushy stuff.
- You Gotta Have Blue Hair
- Zettai Ryouiki: Only once in the anime.
Akira E. Ferrari
- Voiced by: Junko Minagawa (Japanese), Carol Jacobanis (English)
One of the three Water Fairies, Aika's tutor. She's known by the title of "Crimson Rose" for her conversation skill with customers. Tomboyish enough that she can be considered as The Lad-ette.
- Aloof Dark-Haired Girl: She is tall, beautiful, has a number of admirers, mostly female, and behaves in a composed lady-like manner. In front of customers, anyway.
- Can't Hold Her Liquor
- Catchphrase: She often shouts "Suwa!" when the Undines practicing make a mistake.
- Curtains Match the Window
- Drill Sergeant Nasty: Accused of being one, but she's really not that bad... maybe.
- Hard Work Hardly Works: Averted. The only reason she's able to be one of the Water Fairies is because she works really hard. As she said, she has no notable talents like her friends Alicia or Athena have, so hard work is all she can do to make up for it.
- The Lad-ette: Except the drinking part — she can barely hold liquor, especially compared to Alicia, who can hold massive amounts. As a child, she was even more of one, earning the respect of Akatsuki and Woody after they play together, under the assumption that she was a boy.
- Lady Looks Like a Dude: When she was more of a Tomboy, she looked exactly like a regular little boy to the point where strangers were convinced she was one.
- Rapunzel Hair
- Stern Teacher: Akira is regarded as this, but she's also a very good one.
- Tomboy and Girly Girl: The Tomboy to Alicia's Girly Girl.
Ayumi K. Jasmine
- Voiced by: Ryoko Shiraishi
One of the trainees that Akari met when she works at Traghetto. Quite a cheerful person.
- I Just Want to Be Normal: Well, more normal. She doesn't even want to be a Prima at all.
President Hime M. Granzchesta
- Voiced by: Kaori Mizuhashi
Himeya's president. A cat from Manhome. Quite aloof. President Aria has a crush on her.
Azusa B. McLaren
Aika's apprentice in The Avvenire
- Voiced by: Ryo Hirohashi (Japanese), Tarrah Tisch-Wallace (English)
A trainee for Orange Planet. Is considered to be a prodigy because of her gondola skills despite the fact she is still in middle school when she is recruited. A real Deadpan Snarker.
Her Prima alias is "Orange Princess".
- Adorably Precocious Child: She wants to grow up, or at least seem more mature than she lets on. However she can't let her childish tendencies go, such as making games out of her way to school or still adhering to the "good kid/bad kid" morality of the holiday season.
- Alice Allusion
- Catchphrase: She likes to prepend "dekkai" ("huge") to things. This can be translated as "really" or "quite" in most cases.
- Child Prodigy: Nearly flawless rowing skills even when still a pair. She also becomes a Prima before her seniors Akari and Aika.
- Early-Bird Cameo: She appears in the bonus chapter of Volume 2 of Aqua, Lampshaded by both Akari and Aika because her official introduction isn't until Volume 3 of Aria.
- Defrosting Ice Queen: She starts out as this, but mellows out very quickly.
- Grumpy Bear: Rather sour and tries her hardest to be realistic. Her chibi face is even drawn is an eternal scowl.
- Innocent Prodigy: Although hidden under her antisocial personality and her status as a prodigy, she's still shown to have an adorably childlike naivety at times.
- Little Miss Snarker
- Lonely at the Top: While she is grateful for her new job as a Prima, she is upset that the amount of work that she now takes cuts into her time spent with friends, even having no time at all some days.
- Self-Imposed Challenge: She likes to go home from school in various creative ways, such as kicking a rock along the path or only walking on shadows. These often cross into Just a Kid territory.
- Ship Tease: With Woody (only in the manga).
- Shout-Out: Her name is a reference to Lewis Carroll and Alice in Wonderland.
- Sugar-and-Ice Personality: Quite antisocial on the surface.
- Wise Beyond Their Years: Although even with that, she's still 14 and it shows.
- Zettai Ryouiki: In her school uniform.
- Voiced by: Tomoko Kawakami (Japanese), Michele Knotz (English)
One of the three Water Fairies, Alice's tutor. She's known by the title of "Siren" for her beautiful singing voice. Very clumsy, but rather insightful when the chips are down.
- Ambiguously Brown
- Cloud Cuckoo Lander: Even more so than Akari.
- Cute Clumsy Girl
- Dark-Skinned Blonde: The white haired variation of the trope, but still applies.
- Easy Amnesia: Athena suffers a mild case of amnesia after slipping on a banana peel in Orange Planet. She faked it in order to learn what Alice thinks of her.
- Genius Ditz / Obfuscating Stupidity: Is actually capable of not making mistakes, but usually doesn't bother when she's not on the job because it's "too tiring".
- Rapunzel Hair: While she alone of the three Water Fairies has short hair, in the Distant Finale she grows it out.
- Voiced by: Houko Kuwashima
One of the trainees that Akari met when she works at Traghetto.
- Voiced by: Kana Asumi
One of the trainees that Akari met when she works at Traghetto. Very shy.
- Determinator: Has failed the Prima exam several times, but hasn't given up yet.
- Voiced by: Akeno Watanabe (Japanese), Greg Schettino (English)
Orange Planet's president. Originally found as a stray by Alice, who picks her up to take care of. Has a habit of biting President Aria's belly.
- Identical Stranger: She was largely picked up because of her resemblance to Orange Planet's now-deceased former president.
- Pokémon Speak: Inverted, as it's the sounds that inspired the name. She only is able to say "Maa" whenever she speaks.
- Precocious Crush: Has one on President Aria, as revealed during the vet chapter.
- Your Tomcat Is Pregnant: Was thought by Alice to be a male cat until the vet reveals this fact. Without the pregnancy, though.
Alice's apprentice in The Avvenire.
- Glorious Mother Russia: Averted. She has a Russian surname and references Sibera, but doesn't actually know anything about her origins due to being born and raised on Aqua.
He works in one of the floating islands as a Salamander, controlling weather on the planet. Has a crush on Alicia. Akari's first customer.
- Childhood Friends: He and Woody go way back, and they were neighbors and playmates during their childhood. They still occasionally get together and hang out.
- Hopeless Suitor: For Alicia; he is one in a sea of her admirers, and every attempt to woo her goes awry somehow. In addition she is under the assumption that he likes Akari (he does a bit, just not consciously) and often tries to push the two together.
- The Nicknamer: Calls Akari "Pigtails", Aika "Gachapen", and Ayanokouji "Woody".
- Samurai Ponytail: Usually styles his hair this way.
- Ship Tease: With Akari, although he repeatedly states how much he loves Alicia.
- Stalker with a Crush: Mild version for Alicia, mind you.
Ayanokohji Udo the 51st
Better known as Woody, he works as Sylph, an airbike courier delivering goods in a city without streets. Has quite a bad sense of direction.
- Anime Hair: Notable for being one of the few characters to have really crazy looking hair, with his spiked bangs and ponytail.
- Eye Glasses: Both as a kid and as an adult, Woody is seen with a set of round goggles that pretty much act like his regular eyes.
- Nonstandard Character Design: While he is proportional like everyone else, his hairstyle, his lack of eyebrows, and his exaggerated and nearly unchanging face make Woody look very different from the rest of the cast.
- No Sense of Direction: His first appearence has him lose a map and need Akari's help to navigate the city.
- Pair the Spares: Despite not sharing as much screen time with Alice, he often gets ship moments with her in the last leg of the series.
- Transplant: It's either this or he's a descendant of Ayanokohji Udo from Amano's earlier work Roman Club, considering that they have same name, look, and even personality.
- Voiced by: Akeno Watanabe (Japanese), Graham Halstead (English)
A young man working as a Gnome, people who works in gravity control system underground. Aika has a crush on him.
- Don't Explain the Joke: He always does when he makes an-
- Expy: It's almost impossible to not compare his appearance with Harry Potter.
- Huge Girl, Tiny Guy: Has this dynamic with Aika, and it still holds true in the gendebending chapter.
- Older Than They Look: Looks like a cute little boy, even though he's 18. From what we see of the Gnomes in general, it's probably just a side effect of living underground.
- Pun: He often makes "old man" jokes with these. They're so old (and originally from Manhome) that he has to explain them every time.
- Soap Opera Rapid Aging Syndrome: The only logical explanation for him growing at least a foot taller at the end of the final episode but before the timeskip epilogue.
- Stealth Hi/Bye: Happens every now and then.
- Voiced by: Motomu Kiyokawa (Japanese), Mike Pollock (English)
Better known as Mr. Postman, as Akari calls him. Works for the Neo-Venizia post office and gives Akari first trip in gondola. His name is not revealed until near the end of the series.
- Everyone Calls Him "Barkeep": An Omake lampshades this, with everyone calling him not by his name, even though he has a nametag.
- Eyes Always Shut: The only time he opens them is when Akari narrowly avoids crashing, seen here.
Mysterious Mega Neko that appears throughout the work, especially when the supernatural is involved, to Akari especially. Is the King of the Cats of Neo-Venezia, named after the king of the cats of Scottish folklore, and it is strongly suggested he is a guardian spirit of Aqua.
- The Ageless: It's implied that his appearance hasn't changed in centuries, and he has had the role of Casanova for just as long.
- Big Damn Heroes: Saves Akari from the ghost.
- Cat Stereotype: As the Black cat, he is often agreeable and social, and does have a tendency to pop up anywhere in Neo Venezia. He's also associated with good luck and magic.
- Classy Cravat: His normal outfit features a waistcoat and one of these, befitting his proper nature.
- Early-Bird Cameo: He appears in episode 12 of The Animation as Akari crosses the bridge. This is long before he's officially introduced in the anime.
- Four Legs Good, Two Legs Better: Of all the cats shown, he's the only one that is ever shown walking like a Biped. It helps him stand out as the most unusual of the magical cats on Aqua.
- Guardian Entity: Considered one for Neo Venezia.
- Half-Dressed Cartoon Animal: While he is plenty classy in his normal outfit, he neglects to wear pants.
- Hidden in Plain Sight: During Carnivale, he's in the guise of Casanova, one of the largest and most popular characters of the parade. Nobody suspects a thing.
- Invisible to Adults: Urban Legends say that only kids will be able to see Cait Sith, and lose the ability when they finally mature.
- Mega Neko
- The Seven Mysteries: Is actually considered one himself, due to meeting him being an extremely rare event. Akari just got lucky and experienced it 6 times.
- Tsurime Eyes: He is drawn with rather sleek eyes compared to most cats, making him look more mature and wise.
- Supernatural Gold Eyes: Stands out among the important Aquan cats for having these, as opposed to the blue one would expect out of especially magical cats.