Amaru is a fifteen-year-old girl who appears as a main character in the fifth Naruto feature film. She lives in a small village within the Land of Fire and works as an apprentice doctor. Orphaned at a young age, her life changed when she fell ill with a disease that caused the other villagers to shun her out of fear of infection. A traveling healer named Shinno cured her, and in gratitude, she became his student, learning medicine and following him devotedly.

In terms of personality, Amaru is initially presented as determined, energetic, and proud of her medical skills. She has a tomboyish demeanor and is very caring, always looking out for injured people. Her actions are driven by a deep admiration and affection for her mentor, Shinno, whom she trusts completely. However, she is also emotionally vulnerable; her intense feelings of grief and despair are powerful enough to attract a unique entity called the Zero-Tails, which feeds on negative emotions.

Amaru's role in the story begins when the Hidden Leaf Village is attacked by ninjas from the Land of the Sky. She and Shinno are escorted back to their home village by Naruto Uzumaki, Sakura Haruno, and Hinata Hyuga. Upon arriving, she finds her village destroyed, and a series of events leads her to believe Shinno has died saving her life. The overwhelming sorrow and guilt she experiences cause the Zero-Tails to possess her, using her body as a vessel to manifest its dark chakra. The central conflict of the film forces Amaru to confront the truth that her beloved mentor is actually the mastermind behind the attacks, having manipulated her negative emotions for years to feed the Zero-Tails.

Her most significant relationship is with Shinno, whose betrayal shatters her world and nearly drives her to despair. Her bond with Naruto is also key to her development. Despite their initial awkwardness, Naruto refuses to give up on her, even when she is possessed. He helps her find the strength to overcome her sorrow, reminding her that her medical training and desire to help others have real value and are not wasted. Through this, Amaru develops from a grief-stricken girl into a resilient young woman who chooses to save others, even risking her own life to catch a falling Naruto and later helping to rescue the captured villagers from the collapsing flying fortress.

Though she is not a trained ninja, Amaru is quick and agile. Her notable abilities are primarily medical. She demonstrates her skill by treating Naruto after he is bitten by a poisonous fish, and she carries a scalpel for performing minor surgical procedures.