|Alternate Forms||Princess Tutu|
|Anime Debut||The Duck and the Prince|
|Japanese Voice||Nanae Katou|
|English Voice||Luci Christian|
Ahiru is the protagonist of the series. She is a friendly, kind-hearted duck who was given a magic pendant, which turns her into a teenage girl. This pendant also allows Ahiru to turn into her alter-ego, the wise and graceful Princess Tutu.
Ahiru was an ordinary yellow duckling until she saw the prince dancing on the lake and looking lonely. Hearing her desire to bring him happiness, she was given a pendant by Drosselmeyer which gave her the ability to transform into Princess Tutu. If Ahiru removes the pendant or quacks while talking, she transforms back into a duck and must touch water while wearing the pendant to return to her human form.
Later on, to save Mytho, her pendant gives her the power to transform into Princess Tutu. Because she is now a part of Drosselmeyer's story, Ahiru/Tutu will turn into a speck of light and vanish if she confesses her love to Mytho. Nonetheless, Ahiru continues to transform to help return his missing heart shards back to him.
Ahiru is a friendly, kind-hearted character. Like a duck, she is easily excitable, clumsy, and talkative. It is shown in the anime that she can be extremely scatterbrained and uncollected in a nervous situation.
In her human form, Ahiru has muted pink hair with a more noticeable orange tinge that is braided, icy blue eyes, and light skin with freckles. She most commonly seen wearing her school uniform. In two episodes, she wears a casual outfit; a pale yellow turtleneck, khaki shorts, white socks and brown shoes.
When she is transformed into Princess Tutu, she wears a white ballerina dress with light pink lining that has a few blue tails behind it, light pink toe shoes, and a more decorative form of her pendant necklace.
As a duck, she is yellow with bright blue eyes, with one single feather that sticks up at the top of her head. Her human forms share this characteristic, in that a single large stand sticks up like a feather.
During her ballet lessons, unlike the other girls in her class, she wears a light grey leotard that has a dark blue stripe around its waist and a red jewel, similar to her pendant, on the front of its neckline.
Mytho: Ahiru first had a crush on Mytho when she first saw him dancing as a duck. Like most other girls, her crush was mild. Later on, she and Mytho became close friends until Mytho was possessed by the raven's blood. Still, she did not give up on him and helped him conquer the evil Raven.
Fakir: In the beginning of the series, it seems like Ahiru and Fakir dislike each other because Fakir intentionally interrupts Ahiru and Mytho's conversations and the return of Mytho's heart shards by Princess Tutu. However, this is quite possibly because Fakir is jealous of Ahiru's interactions with Mytho. They both begin to develop affection for each other throughout the series. In the episode "Dreaming Aurora" when Paulamoni requests to observe Ahiru dance, Fakir immediately volunteers to dance the Pas de Deux with Duck when Rue suggests that Mytho should. Although their very short and whispered conversation isn't very polite, Ahiru blushes intensely when Fakir holds her against his chest and up in the air. Fakir realizes that Ahiru is Princess Tutu the night that she tells him that she has no desire to fight with him when he sees Duck sneaking around the dorms shortly after the encounter and recognizes the pendant on her chest. When he confronts her about this, she admits she feels relieved that he knows and begins to have more positive and intimate thoughts about him. In the episode "Banquet of Darkness" Ahiru admits to Fakir that she doesn't know why she likes Mytho, that she just thought he was handsome and that she just wants to return the heart shards to him. In this same episode, Fakir and Ahiru are seen swimming side-by-side, Fakir staring intently at their joined hands. Near the end of the series, it is revealed that Fakir is a direct descendant of Drosselmeyer and that he has the power to write stories that come true; however, he can only write stories about Ahiru and continues to do so to save and protect her. Fakir initiates an intimate dance with Ahiru in the Lake of Despair and vows to stay by her side forever.
Rue: Ahiru admires Rue as an advance class student, and often tries to reach out to her as a friend. The first time she ever truly interacted with Rue was when she and her did a pas de deux together after getting to know each other. When Rue becomes Princess Kraehe, Ahiru kept faith that the kind Rue she knew was not lost forever.
- Ahiru means Duck in English.
- She is not a duck in the manga, although she is briefly turned into one.
- In the manga, her last name is mentioned being Arima.
- Her English voice actress, Luci Christian who previously voiced Hibari Hanakoganei from the manga and anime series, Cyberteam of Akihabara.
- Interestingly, both Ahiru and her alter-ego Princess Tutu are much sounded like Hibari's.