Ahiru, also known as Duck, begins as an ordinary duck who witnesses a heartless prince dancing alone by a lake and feels profound pity for his solitude. This draws the attention of Drosselmeyer, the story’s author, who gifts her a magical pendant. The pendant enables her to transform into a human girl and further into the mythical ballerina Princess Tutu. Her central motivation is to see the prince smile—a goal she holds so dearly she is willing to sacrifice her life for it. The pendant is essential for maintaining her human form; if removed or if she makes a duck-like sound, she reverts to her original duck form. To become human again, she must touch water while wearing the pendant. A crucial condition of her existence as Princess Tutu is that confessing her love to the prince will cause her to vanish into a speck of light. In human form, she stands 150 cm tall with coral-colored hair often styled in braids and a prominent cowlick, blue eyes, light skin with freckles, and typically wears her school uniform or casual outfits reflecting the color palette of her duck form. As a duck, she is a small yellow duckling with blue eyes and a single feather sticking up from her head. Her personality combines friendliness, kind-heartedness, energetic clumsiness, and naivety. She is excitable, scatterbrained, talkative, and prone to quacking when overexcited. She often struggles with self-doubt and second-guesses her actions, criticizing herself for her perceived flaws. Yet she also exhibits deep compassion, determination, and a readiness to help others and do what is right, even at great personal risk. Her kindness extends selflessly even to those who treat her as an enemy. Over time, she grows more determined and willing to take risks for her friends. As a ballet student at Gold Crown Academy, she is notably unskilled and clumsy in her human form, frequently arriving late to class. In contrast, her transformation into Princess Tutu grants her grace, wisdom, and exceptional ballet skill. Her mission as Princess Tutu is to find the scattered shards of the prince’s shattered heart and return them to him along with their associated emotions, often through dance, which helps release the feelings trapped within the shards. Her relationships develop significantly. Her initial admiration for the prince, Mytho, is based on his appearance rather than deep knowledge, but evolves into a selfless, devoted affection focused on his happiness. Her relationship with Fakir begins with tension and dislike due to his harsh treatment and possessive protection of Mytho, but grows into a strong partnership and deep mutual affection, with Fakir becoming her source of strength and vowing to always stay by her side. She deeply admires Rue for her ballet skill and consistently believes in the kind person beneath her alter ego, Princess Kraehe, considering her a friend despite their rivalry. A major arc involves her questioning her own identity and feelings. She wonders whether her true self is the duck, the girl, or Princess Tutu, and grapples with insecurities about her clumsiness and mission. She eventually realizes her love for Mytho is about his happiness rather than romantic possession, separating herself from the predetermined role of Princess Tutu. This leads to a confrontation with Drosselmeyer, where she defiantly asserts that her feelings are her own and she is not a marionette, claiming her free will against his tragic narrative. The climax of her story involves a significant sacrifice. She discovers her pendant is the final shard of Mytho’s heart. After initial hesitation driven by fear of losing her human form and ending the story, she finds the courage to remove it, permanently reverting to a duck and fully restoring the prince’s heart. In the final battle, though injured and unable to transform, she continues to dance, inspiring the townspeople to reclaim their stories. This defiance, supported by Fakir’s writing, helps defeat the Raven. In the end, she accepts her identity as a duck and remains with Fakir as he writes a new story, while Mytho and Rue return to their kingdom. In the manga adaptation, where she is named Ahiru Arima, her story differs. Her feelings for Mytho are more open-ended, with Rue presented as a direct rival for his affections. Drosselmeyer does not appear, and Edel takes on a role more similar to his, reportedly plotting to revive the Raven within herself.