The highly anticipated anime film adaptation of Nowaki Fukamidori’s fantasy mystery novel, “Whoever Steals This Book” (Kono Hon o Nusumu Mono wa), officially premiered in Japan on December 26, 2025. This reveal comes after earlier announcements detailing the film’s staff and studio, with recent updates showcasing the full main cast and the captivating theme song. Originally slated for a 2026 release, the film was brought forward to conclude the year with its unique literary adventure.
A Deep Dive into the Narrative: Plot and Premise
“Whoever Steals This Book” centers on Mifuyu Mikura, a high school student with an unusual disdain for books, a stark contrast to her family’s legacy of avid book collecting and their ownership of the esteemed Mikura Hall library. Her life takes an unexpected turn when a theft at Mikura Hall triggers an ancient “book curse.” This magical phenomenon transforms her entire town, turning it into the vivid settings of the stolen novels and casting its residents into the roles of the stories’ characters.
To break the curse and restore her town to normalcy, Mifuyu must embark on a perilous journey to reclaim the stolen books, venturing directly into the very stories she once despised. She is not alone in this literary quest; a mysterious girl named Mashiro acts as her guide, helping her navigate the enchanted, genre-hopping world.
The Voices Behind the Characters: Main Cast Revealed
The film boasts a talented ensemble bringing the characters to life. Leading the cast is Rin Kataoka as the reluctant protagonist, Mifuyu Mikura. Joining her on this fantastical adventure is Sora Tamaki as the enigmatic Mashiro.
Key supporting roles include:
- Nao Toyama as Hirune Mikura
- Junichi Suwabe as Ayumu Mikura
- Shizuka Ito as Keiko Yosano
- Shimba Tsuchiya as Takafumi Haruta
- Romi Park as Tamaki Mikura
Further expanding the cast, recent announcements confirmed Inori Minase as Mifuyu’s late mother, Kazune Mikura, Akio Ōtsuka as a coffeehouse owner, Shun Horie as “Tori no Negima” (Chicken and Onion Skewer), and Masaya Matsukaze as a coffeehouse regular. Other notable cast members include Shigeru Chiba, Ryōta Suzuki, Reina Ueda, Tomokazu Seki, Rie Takahashi, Yō Taichi, Makoto Koichi, Yumiri Hanamori, Hitomi Ueda, Manaka Iwami, and Jun Fukuyama.
Creative Team and Production Studio
The anime film is a production of Studio Kagokan, a relatively new studio founded in 2022, marking “Whoever Steals This Book” as its first full-length feature. Daisei Fukuoka (also cited as Daiki Fukuoka), known for his work on the Radiant series, directs the film. The screenplay is penned by Yasuhiro Nakanishi, recognized for his contributions to Kaguya-sama: Love is War.
Veteran animator Keiko Kurosawa handles the character designs and serves as the chief animation director, ensuring a consistent and visually impressive style. The musical score, which will undoubtedly play a crucial role in conveying the film’s genre-hopping essence, is composed by Michiru Ōshima. Yuji Higa, founder of Kagokan, serves as the animation producer, with Kadokawa Animation distributing the film.
The Melodies of the Adventure: Theme Song
Adding another layer to the film’s appeal is its theme song, “Share,” performed by the acclaimed artist YUKI. The song was prominently featured in a new trailer released on October 16, 2025, giving audiences a taste of the film’s auditory landscape alongside its visual spectacle.
From Pages to Screen: The Origin Story
The film is an adaptation of Nowaki Fukamidori’s novel, which was first published by Kadokawa Shoten in October 2020, with a paperback edition following in June 2023. The story also received a manga adaptation, illustrated by Kakeru Sora, which was serialized in Kadokawa Shoten’s Young Ace magazine from December 2021 to March 2023, spanning three tankōbon volumes. Yen Press licenses both the novel and manga in English, allowing international audiences to delve into Mifuyu’s world.
