An Idol Scoring His Own Film
There's something neat about a lead actor whose group also handles the theme song. Satō Shori voices protagonist Natsume Makoto in this adaptation of Mado Kaori's light novel, and timelesz — the group he's been part of since their days as Sexy Zone — wrote "Kienai Hanabi" (roughly "Fireworks That Never Fade") specifically for the film.
"Fireworks might be a moment's brilliance," Satō said in comments reported by Anime Anime. "But they're also something that stays deep in your heart forever. I think we managed to capture that in this theme song."
The film adapts Mado Kaori's novel, published under Shogakukan's Gagaga Bunko imprint. Set against the backdrop of the Nagaoka Festival Grand Fireworks — one of Japan's three largest fireworks events, drawing hundreds of thousands of visitors to Niigata each summer — the story follows high schooler Natsume Makoto after a classmate named Hayama Aki (葉山煌) tells him "I've always wanted to meet you." A single fireworks painting pulls Makoto to Nagaoka, where he meets Haru, a girl who appears to have wandered in from the past. What unfolds is a love story spanning 81 years, built around a promise that slowly comes to light.
The Cast Behind the Fireworks
Hara Nanoka, best known as the voice of the title character in Makoto Shinkai's Suzume, plays heroine Hayama Aki. Alongside the theme song reveal, Anime Anime confirmed two new cast additions.
Rie Takahashi (Emilia in Re:Zero, Megumin in KonoSuba) voices the mysterious Haru — a girl seemingly displaced from the past. Takahashi noted that tackling the Nagaoka dialect was a first for her. "I started by learning from the guide audio in the recording footage, and on the day of recording, people from Nagaoka watched over us as we worked through it," she said, calling the experience "dense and rewarding." She described Haru as "strange but full of very sincere feelings" and encouraged audiences to share the same moment in time with the characters.
Comedian Natsuko Yokosawa rounds out the newly announced cast as Makoto's mother, Natsume Yukari. Yokosawa hails from Niigata Prefecture, making the casting a hometown connection. She was told to channel "a working hair-and-makeup mom who's always watching over her son," and said she hopes her performance helps push Makoto forward in his journey.
The film is directed by 鈴木慧 (likely read Suzuki Kei), with a script by Mori Kōhei. Animation production is handled by SynergySP and Answer Studio, with Shin-Ei Animation — the studio behind Doraemon and Crayon Shin-chan — serving as producer. Distribution runs through Shochiku and Shin-Ei Animation, with backing from Niigata Prefecture, Nagaoka City, and the Nagaoka Fireworks Foundation.
Looking Ahead
Kimi to Hanabi to Yakusoku to opens in Japanese theaters on July 17, 2026. No international distribution or streaming partners have been announced. The source novel is published by Shogakukan under the Gagaga Bunko label, but no English-language release has been confirmed.
A main trailer has been produced, and promotional materials continue to roll out ahead of the summer premiere. With the full voice cast now locked and the theme song in place, the remaining question is whether this time-spanning Nagaoka romance can land with summer audiences the way its fireworks-lit premise promises.