MERMAID MELODY: PICHI PICHI PITCH

As the mermaid princess of the North Pacific (one of the seven mermaid kingdoms), Lucia entrusts a magical pearl to a boy who falls overboard a ship one night. Lucia must travel to the human world to reclaim her pearl and protect the mermaid kingdoms. Using the power of music Lucia is able to protect herself and the mermaid kingdoms from a growing evil force. — Description from AniList community (anilist.co).