Eiga Chiikawa: Ningyo no Shima no Himitsu (Chiikawa Movie: Secret of the Mermaid Island) continues its historic box office performance across Japan. Having premiered on July 24, 2026, the theatrical feature has amassed 14.66 billion yen (approximately $100 million USD) and over 10 million viewers within its first 52 days in theaters.
Box Office Milestone & Novel Theater Bonus
Adapting the dark fantasy turned fan-favorite Siren Arc from creator Nagano's viral X (formerly Twitter) manga, the film has sustained immense theatrical momentum. Following special 4DX screenings and interactive cheer screenings, the production committee announced the fifth theatrical visitor gift: a 52-page physical booklet titled Himitsu Bon (Secret Book).
The booklet collects rare production materials directly from Nagano's initial planning stages. Highlights include early Siren Arc concept sketches revealing alternate narrative directions—such as substituting Siren with the character "Ano Ko" or featuring voiced lines and distinct faces for Hitoha and Futaba. Additionally, the booklet features a brand-new short manga titled Ode to Shima depicting a brawl between Shimajiro and Ode, alongside Nagano's newly illustrated essay manga Muchaguma Nikki.
Distribution of the limited-edition booklet begins in participating Japanese theaters on September 19, 2026. The franchise is also expanding its multimedia push with official animated and voiced LINE sticker sets capturing iconic dialogue from the feature film.
