One year ago, Yūta lost his father in a car crash. Now in the 6th grade, Yūta goes to catch beetles in a dam near a mountain, a place he often went with his father. There, Yūta meets a strange old man, and while walking in heavy rainfall, slips and blacks out. When Yūta awakes, he sees a child, Saeko, who shows him a village from the past. A precious summer vacation for Yūta begins.
Unfortunately the movie Rainbow Fireflies is not yet available on HBO Max.
| Directing | Konosuke Uda | Director |
| Sound | Masataka Matsutōya | Original Music Composer |
| Sound | Otohiko Fujita | Musician |
| Visual Effects | Takaaki Yamashita | Layout Supervisor |
| Art | Hideki Nakamura | Background Designer |
| Writing | Kunii Katsura | Screenplay |
| Visual Effects | Hisashi Mori | Animation Director |
| Art | Yutaka Ito | Background Designer |
| Art | Yoshikatsu Matsumoto | Background Designer |
| Visual Effects | Tomoaki Takase | Key Animation |
| Art | Kaori Hino | Background Designer |
| Art | Atsushi Morikawa | Background Designer |
| Art | Junichi Taniguchi | Background Designer |
| Art | Tomotaka Kubo | Background Designer |
| Art | Ayami Hidaka | Background Designer |
| Art | Tomoko Zama | Background Designer |
| Visual Effects | Shuntaro Mura | Key Animation |
| Visual Effects | Tetsuro Kaku | Key Animation |
| Art | Takanori Tanaka | Background Designer |
| Visual Effects | Takayuki Hamada | Key Animation |
| Art | Akira Kuramoto | Background Designer |
| Art | Akio Shimada | Background Designer |
| Art | Masaki Yoshizaki | Background Designer |
| Visual Effects | Yoshihiro Kitano | Key Animation |
| Visual Effects | Seiki Tamura | Color Designer |
| Art | Sagako Itakura | Background Designer |
| Art | Nizou Yamamoto | Background Designer |
| Visual Effects | Hisashi Mori | Character Designer |
| Art | Seiki Tamura | Art Direction |
| Visual Effects | Kouichi Arai | Key Animation |
| Visual Effects | Ikuo Kuwana | Key Animation |
| Visual Effects | Kagetsu Aizawa | Key Animation |
| Visual Effects | Hisashi Mori | Key Animation |
| Visual Effects | Hidemi Kubo | Key Animation |
| Art | Sadahiko Tanaka | Background Designer |
| Art | Kentaro Akiyama | Art Designer |
| Visual Effects | Hiromi Ishigami | Key Animation |
| Art | Reiko Okada | Background Designer |
| Visual Effects | Tatsuzo Nishita | Key Animation |
| Visual Effects | Ryo Onishi | Key Animation |
| Art | Midori Tanaka | Background Designer |
| Art | Katsu Nozaki | Background Designer |
| Visual Effects | Ikuko Ito | Key Animation |
| Visual Effects | Takashi Mukouda | Key Animation |
| Visual Effects | Shinji Hashimoto | Key Animation |
| Visual Effects | Shinya Kitamura | Key Animation |
| Art | Nagisa Nishida | Background Designer |
| Visual Effects | Shinya Ohira | Key Animation |
| Art | Shu Imai | Background Designer |
| Visual Effects | Hirofumi Masuda | Key Animation |
| Visual Effects | Yoshiyuki Ito | Key Animation |
| Art | Yuka Kawai | Background Designer |
| Art | Hitoshi Nagasaki | Background Designer |
| Visual Effects | Naoki Tate | Key Animation |
| Visual Effects | Hokuto Sakiyama | Key Animation |
| Visual Effects | Hideaki Maniwa | Key Animation |
| Art | Yoshiaki Honma | Background Designer |
| Visual Effects | Miyako Kitada | Key Animation |
| Visual Effects | Shigeru Kimishima | Key Animation |
| Visual Effects | Kenichi Konishi | Key Animation |
| Visual Effects | Shinya Inoue | Key Animation |
