Lu over the Wall

Kai Ashimoto is a middle school student who lives with his father and grandfather in Hinashi, a quiet fishing village. He used to live in Tokyo, but after his parents divorced he moved to his father's hometown. Kai struggles to express his feelings to both of his parents. He felt lonely and depressed by his school life. He only finds comfort by uploading songs composed by himself to the internet. One day, his classmates Kunio and Yuho invited him to join their band, "SEIREN". When they arrive at the practice site on Ningyojima Island (Merfolk), a mermaid named Lu appears in front of them. Since ancient times, the townspeople of Hinashi believed that mermaids would bring calamity. Hinashi City is in danger. Can Kai's conscience save this city?