Lu Over The Wall 2017

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.