The series begins with a love story between Kim Dam Reung and the Seahorse Mermaid. When Kim sank into the sea, he was rescued by the mermaid called Si-hwa and became friends. After a long time, friendship between them became a violent love story. One day, Kim's family decided to marry another girl, and Si-ha received the news of Kim's marriage from another girl with great shock. She decided to erase all her memories and love to start her life again but fate brings them back to live a deep love story, an extraordinary love story.