Kaguya Shinomiya is a main protagonist of this anime film, which continues directly from the end of the third television season. She is a third-year student at the prestigious Shuchiin Academy and serves as the student council vice president. As the eldest daughter of the vast and powerful Shinomiya conglomerate, she is a prodigy who excels in academics, martial arts including judo and aikido, and traditional arts like kyudo, in which she competes at a national level. Her public image is that of a beautiful, untouchable heiress, a perception that hides a much more complex and vulnerable interior world.

Born as the child of her father’s affair with a woman named Nayotake Shimizu, who died shortly after Kaguya’s birth, her position within the Shinomiya family has always been precarious. This upbringing, marked by emotional neglect and intense pressure to perform, fostered a cold, calculating, and distrustful personality. In her middle school years, she was known as the Ice Princess Kaguya, a persona defined by emotional suppression and a ruthless, logical approach to social interactions. She developed a habit of testing potential friends by sharing secrets to see if they would be leaked, a practice born from a deep-seated fear of betrayal. Only Chika Fujiwara successfully passed this test and became her first true friend.

In the present, Kaguya is deeply in love with the student council president, Miyuki Shirogane. However, her immense pride and fear of rejection prevent her from confessing. The central conflict of the film arises after their long-awaited first kiss at the school festival; instead of bringing simple happiness, the event triggers a severe emotional regression. Overwhelmed by the stress of her feelings and the daunting future, she reverts to her Ice Kaguya personality. In this state, she becomes highly passive-aggressive and toxic, expecting Shirogane to read her mind and understand her unspoken needs while punishing him for his failure to do so. This internal conflict reveals her deepest desire: not for extravagant romance, but for an ordinary, normal relationship where she can be fully vulnerable and accepted for all her flaws, without having to pretend.

Throughout the film, Kaguya battles the different facets of her own psyche, including the logical but cold Ice Kaguya and a more childish, foolish side that represents her suppressed desire for happiness and ease. Her character development in this story is about learning to lower her defenses and communicate openly, moving beyond the intricate mind games that defined her earlier relationship with Shirogane. Her key relationships are central to this struggle: her bond with Shirogane is tested as they must learn to be honest with each other; her friendship with Chika Fujiwara remains a source of warmth and normalcy, even as Chika remains oblivious to the depths of Kaguya’s romantic turmoil; and her role as a supportive senior to Yu Ishigami continues to show her capacity for genuine kindness. Despite her genius-level intellect, she is notably naive about common technology, having only recently switched from a flip phone to a smartphone, and she possesses an innocent, often uninformed understanding of romance and sexuality.