Natsume Amano is a thirteen-year-old junior high school student who becomes the central human protagonist of the story. She is the daughter of Keita Amano, the original Yo-kai Watch wielder, and his wife Fumika. When Natsume was young, she nearly drowned in a river and was mysteriously saved by a figure she did not recognize, an event that leaves her with a key-shaped charm she treasures. As the narrative begins, she displays a naturally helpful and selfless personality, stopping to rescue a drowning child even as strange events unfold around her. She is described as a caring and pure-hearted girl who cannot ignore people in need, and she is chosen by the Yo-kai Watch Elda, a new watch that selects its wielder independently. This watch is given to her by Whisper, who has been testing candidates to combat the spread of the Onimaro virus. Using the Elda, Natsume can summon Yo-kai through items called Yo-kai Arks and transform them between their standard Lightside forms and their more aggressive Shadowside forms, which are suited for combat. Her initial motivation is to protect her family and community after the Onimaro infect her own mother and younger brother, turning them into Kaodeka Oni. She later takes on a larger mission to stop the Oni King Rasen and the Onimaro leader from destroying the balance between the human world and the Yo-kai World. Over the course of the film, she forms key bonds with her two main allies: Touma Tsukinami, a classmate who initially allies with the Onimaro due to his loneliness but is redeemed and befriended by Natsume, and Akinori Arihoshi, a young trainee shaman who provides expertise on supernatural matters. Together with them, she works to free Touma from the Onimaro's control and ultimately confronts Rasen. During the final battle, she is thrown into the sea, but her charm is revealed to be a Yo-kai Ark that summons Seiryuu, the same Yo-kai who saved her as a child. With Seiryuu and other Yo-kai she summons, she helps break Rasen's armor, allowing Touma to deliver the final blow. Natsume's personal development involves growing from an ordinary, albeit brave, schoolgirl into a determined fighter who accepts her role as the Elda's wielder. She also comes to understand that her connection to the Yo-kai world runs deeper than she knew, as later revelations in the broader Shadowside series tie her to a past incarnation named Shuka. In terms of abilities, her primary power is the Yo-kai Watch Elda, which allows her to activate Yo-kai Arks and command a wide variety of Yo-kai in battle. She can switch them between Lightside and Shadowside forms to adapt to different combat situations. Her natural empathy and resolve make her an effective leader among her peers, even as she relies on the strength of the Yo-kai she befriends.