Lady Himi is a young woman who appears in the fantastical tower world that the protagonist Mahito Maki enters. She is a supporting protagonist in the story. She possesses the ability to cast flame magic, which she uses to fend off monsters and predatory animals within that realm. Her pyrokinetic powers are granted by the world stone found in the tower. She is first encountered protecting bubble-like spirits called Warawara from being eaten by pelicans. Later, she rescues Mahito from the man-eating parakeets that inhabit the world. She assists him in his quest to find his missing stepmother, Natsuko, and shows him a counterpart of the tower that contains doors leading to many different times and places. Her personality is spirited and brave. She acts with confidence and a sense of purpose, contrasting with the tragic fate she knows awaits her. As the story unfolds, it is revealed that Lady Himi is a younger version of Mahito's birth mother, Hisako, who entered the tower world during her own childhood. This revelation deepens her role from a helpful ally to a figure of profound personal significance for Mahito. Their bond is protective and affectionate, shaped by the unusual circumstance of a son meeting his mother as a girl. Her primary motivation is to protect the innocent beings within the tower world, and later, to help Mahito on his journey. When she learns her true identity, she chooses to return to her own time through a specific door. She is fully aware that doing so means she will eventually die in the hospital fire that opens the film, but she accepts her fate without worry because it allows her to give birth to Mahito and live the life that leads to him. Her development is tied to this act of acceptance, showing a quiet courage and selflessness. Her notable abilities include her flame-based combat magic, her knowledge of the tower world's geography and its many doors, and her deep emotional resilience in the face of her own mortality. She serves as a catalyst for Mahito's emotional resolution, allowing him to find closure regarding his mother's death and to embrace his new family.