憑獨特的視覺效果聞名的湯淺政明，以首部原創劇場版動畫在「動畫界奧斯卡」勇奪最佳動畫長片！故事講述住在蕭條小漁村日無町的初中生海，靠在網路公開自己創作的音樂提高名氣，與同學一齊組band，在人魚島上練習時竟然與人魚少女露相遇。但是，村中一直流傳人魚是詛咒，海與人魚如何拯救漁村呢？鬱悶的海和露每天相處，漸漸地解開了自己心防，由年僅15歲的報知電影賞新人下田翔大首次為動畫配音，兼自彈自唱錄製主題歌，露則由《你的名字。》四葉的聲優谷花音負責，連柔道運動員篠原信一也參與配音演出。

Taking the top prize at the Annecy International Animation Film Festival, Yuasa Masaaki’s first original feature film unfolds a magical, pop music-infused fantasy produced entirely in flash animation. After his parents’ divorce, Kai moves from Tokyo to the sleepy fishing town of Hinashi. The gloomy teen’s one joy is creating and uploading his own music, which attracts the attention of enthusiastic classmates Kunio and Yuho. When Kai reluctantly joins their band practice on a nearby island, he encounters a curious young mermaid named Lu whose gleeful interest in his music will turn his world upside-down.