Suiheisen no Nella

Synopsis

In a seaside town, a young girl living with her fisherman grandfather encounters a mysterious blue-eyed young man on the day of a great tide. He claims to be searching for a mermaid. Several years later, he appears before her again, looking exactly the same as before. Then, on the night of another great tide, she is mysteriously drawn into the sea. (Source: Natalie, translated)