Ahiru begins as a simple duck witnessing Prince Mytho dancing alone by a lake, radiating profound loneliness. Moved to ease his isolation, she receives a magical pendant from the deceased storyteller Drosselmeyer. This artifact transforms her into a human girl of roughly fourteen, featuring coral-colored braided hair, blue eyes, and light freckled skin. It also allows her to become Princess Tutu, a graceful and empathetic ballet-dancing heroine. Crucially, the pendant holds the final shard of Mytho's fractured heart. Maintaining human form requires wearing the pendant and suppressing duck-like behaviors, especially quacking; breaking this rule reverts her to a duck, requiring water contact while wearing the pendant to regain human shape. A pivotal narrative rule dictates that confessing love to Mytho as Princess Tutu would cause her to vanish into light. Her personality reflects persistent kindness, optimism, and compassion, often shown through selfless acts for others. However, she displays pronounced clumsiness, excitability, and frequent self-doubt, particularly about her ballet skills in human form and her conflicted identity across forms. Despite these insecurities, she exhibits unwavering determination and courage when facing threats to friends or the town. Her internal conflict shifts from initial idolization of Mytho towards questioning her purpose within Drosselmeyer's story, culminating in her asserting autonomy over her feelings and directly rejecting her predetermined fate as a narrative pawn. Relationships drive her journey. Her initial infatuation with Mytho, born from admiration of his beauty and loneliness, matures into selfless dedication to restoring his emotional wholeness without romantic expectation. Antagonism with Fakir, Mytho's protective roommate, evolves into deep mutual trust and partnership. This change starts when Fakir discovers her secret identity and returns her lost pendant, deepening through their joint efforts to protect Mytho and confront the Raven. Their bond becomes one of reciprocal emotional dependence, with Fakir's commitment proving vital during her lowest moments. With Rue, the advanced ballet student and Mytho's assumed girlfriend, Ahiru persistently offers friendship despite Rue's hostility and transformation into the antagonistic Princess Kraehe. Ahiru maintains faith in Rue's inherent goodness, ultimately witnessing Rue's redemption through sacrifice. Supportive friendships with classmates Pike and Lilie, plus mentorship from the puppet Edel, further reinforce her empathy. Her development centers on rejecting predetermined roles. Initially compliant within Drosselmeyer's tragic narrative, she increasingly questions her purpose, especially as Mytho succumbs to the Raven's blood. This leads her to confront Drosselmeyer, declaring ownership of her feelings and rejecting her status as a marionette. Her understanding of love evolves beyond romantic fixation on Mytho towards a broader, empowering compassion inspiring collective resistance against despair. During the Raven's resurrection, she relinquishes the pendant—the final heart shard and her tether to humanity—enabling Mytho's restoration. Severely injured while rallying the townspeople against the Raven through sheer persistence, she draws upon Fakir's written encouragement to manifest Princess Tutu one final time without magical transformation. This act purifies the town and aids the Raven's defeat. Accepting permanent duck form signifies self-acceptance, as she finds contentment remaining with Fakir, who continues writing new stories. In the manga adaptation, named Ahiru Arima, core elements like her duck origin, pendant, and transformations remain. However, her romantic trajectory lacks resolution, leaving feelings for Mytho ambiguous and reducing Fakir's role in her development. The narrative emphasis diverges, with Edel adopting a more antagonistic role aligned with Raven revival plots absent from the anime. Her abilities remain intrinsically linked to Drosselmeyer's pendant. Human morphing permits duck-to-girl transformation under strict behavioral conditions. Heroine Mode activation enables transition into Princess Tutu, whose ballet skill and empathetic connection to heart shard bearers facilitate retrieval. Tutu's grace does not transfer to Ahiru's human ballet skills. These powers cease permanently upon surrendering the pendant during the finale.