Yoake Tsugeru Lu no Uta is Yuasa's first anime film with an original story. The protagonist Kai moves with his father from Tokyo to the declining fishing town of Hinashi to live with his grandfather following his parents' divorce. Kai is unable to give words to his complex feelings about his parents, so he passes his middle school life gloomily. His one joy is uploading his musical compositions to the internet.
One day his classmates Kunio and Yūho invite him to join their band, and when he reluctantly accompanies them to practice on Mermaid Island, the three of them meet a mermaid named Lu. Through her cheerful singing and dancing, Kai is slowly able to open up about his feelings. However, calamity strikes and Kai must shout from the bottom of his heart in order to save the town.
Kanon Tani (your name.) and Shōta Shimoda are starring in the film as Lu and Kai, respectively. Shinichi Shinohara plays Lu's father and the comic duo Chidori play fishermen. Other cast members include Akira Emoto as a grandfather, Sōma Saitō as Kunio, and Minako Kotobuki as Yūho.
Yuasa is directing the film at his Science SARU studio, and is collaborating with Reiko Yoshida (Non Non Biyori, Tamako Market) on the script. Yōko Nemu (Gozen 3-ji no Muhōchitai) is providing the original character designs, and Nobutake Ito (Kaiba, Ping Pong) is adapting the designs for for animation and serving as animation director