timelesz’s ‘Kienai Hanabi’ Selected as Theme Song for Anime Film ‘Kimi to Hanabi to Yakusoku to’ Starring Sato Shori

The idol group timelesz’s new song ‘Kienai Hanabi’ has been selected as the theme song for the anime film ‘Kimi to Hanabi to Yakusoku to’. In this film, group member Sato Shori plays the protagonist Natsume Makoto, marking his first lead role in an anime film. The film will be released nationwide in Japan on July 17, 2026.

The original work is the novel ‘Kimi to Hanabi to Yakusoku to’ by Madorika, published by Shogakukan under the Gagaga Bunko label. The story is set against the backdrop of the Nagaoka Festival Grand Fireworks Display, one of Japan’s three major fireworks festivals, which attracts hundreds of thousands of visitors annually. It depicts a fleeting and poignant love story that transcends time, connected by a single drawing of fireworks.

The heroine Hayama Kira is voiced by actress Hara Nanoka.

Further, it was announced that Takahashi Rie will voice the mysterious girl Haru, and Yokozawa Natsuko, a native of Niigata Prefecture, will voice Makoto’s mother Natsume Yukari. Takahashi said, ‘This was my first time trying the Nagaoka dialect, so I first learned from a guide audio embedded in the recording footage, and on the day, I recorded while being checked by people from Nagaoka.’ Yokozawa commented, ‘It is an honor to be part of a wonderful work from my hometown of Niigata.’

The theme song is the newly written song ‘Kienai Hanabi’ by timelesz. Sato said, ‘Fireworks may be a momentary brilliance, but they also leave feelings deep in the heart forever. I think we were able to create such a theme song.’

The story begins when Natsume Makoto, shortly after entering high school, is approached by classmate Hayama Kira who says, ‘I’ve wanted to meet you for a long time.’ He follows the mystery of a single drawing of fireworks and visits the town of Nagaoka, where he meets a girl named Haru who has wandered from the past. The past and future intertwine, and the truth of a ‘promise’ made across 81 years is revealed.

The director is Suzuki Kei, the screenplay is by Mori Kouhei. Animation production is by SynergySP and Answer Studio. Distribution is by Shochiku and Shin-Ei Animation. Supporters include Niigata Prefecture, Nagaoka City, and the Nagaoka Fireworks Foundation.

The film ‘Kimi to Hanabi to Yakusoku to’ opens nationwide on July 17, 2026.

Full Comments

Sato Shori and Hara Nanoka

●Sato Shori (timelesz) as Natsume Makoto
Movie ‘Kimi to Hanabi to Yakusoku to’ theme song selected timelesz’s ‘Kienai Hanabi’. The work is truly wonderful, so I felt pressure… But just as Makoto and Kira met, I was able to encounter this song. I can deliver it with confidence.
Fireworks may be a momentary brilliance.
But they also leave feelings deep in the heart forever.
I think we were able to create such a theme song.
I hope it reaches everyone.

●Takahashi Rie as Haru

Hara Nanoka

Haru (Takahashi Rie)

I was honored to be entrusted with a role that is interesting and has backbone. Through this work, I myself learned about Nagaoka, so I feel a kind of sense of mission in delivering it as a theatrical animation that many people will see.
The Nagaoka dialect was a first for me, so I first learned from a guide audio embedded in the recording footage, and on the day, I recorded while being checked by people from Nagaoka. During the recording, there were expressions that some people in Nagaoka use and others don’t, and for newly added lines, they acted them out for me.
It was an intense experience to record while being close to Nagaoka! Looking at the description of Haru, the role I’m in charge of, it says she ‘seems to have wandered from the past’…! It’s a mysterious but very straightforward story. Please come to the theater and share the same time as them.

●Yokozawa Natsuko as Natsume Yukari

Yokozawa Natsuko

Natsume Yukari (Yokozawa Natsuko)

I am honored to be part of a wonderful work from my hometown Niigata. I played the role of Makoto’s mother, and during the recording, I was told ‘Imagine a working mom who works hard as a hair and makeup artist.’ I was nervous about whether I could produce a voice that watches over her son while working. I was moved by Makoto’s straightforwardness, and I hope I can support him well. I hope that Makoto’s passionate running through his story will reach many people.

Work Information

• Title: ‘Kimi to Hanabi to Yakusoku to’
• Release: July 17, 2026 (Fri)
• Cast: Sato Shori (timelesz), Hara Nanoka, Takahashi Rie, Yokozawa Natsuko
• Theme song: timelesz ‘Kienai Hanabi’
• Original: Madorika ‘Kimi to Hanabi to Yakusoku to’ (Shogakukan Gagaga Bunko)
• Director: Suzuki Kei / Script: Mori Kouhei
• Animation Production: SynergySP / Answer Studio
• Distribution: Shochiku / Shin-Ei Animation
• (c) Movie ‘Kimi to Hanabi to Yakusoku to’ Production Committee