Lu Over the Wall (2017)

Lu is a rare twin-tailed mermaid who loves music; when middle schoolers Kai, Yuho and Kunio secretly practice their indie-pop music on Merfolk Island, a pile of rocks near the fishing village of Hinashi, Lu cannot help but dance! Her tails turn into legs and she becomes a swirling dervish of movement. She also wants to be friends with everyone, but the people of Hinashi have many old tales about the merfolk, including that they eat people, and Lu may be in danger from those humans if the teenagers can't save her…. This is a lovely animated film, very colourful and with a mostly upbeat story line that young children would probably enjoy very much. All that, plus J-pop music too; a real winner!