Haeseo is deeply moved when the little boy he saved long ago, Taegun, returns to the seaside where they first met as an adult.
Although Haeseo reunites with Taegun in his human form, a mistake reveals the truth that Haeseo is actually a mermaid to Taegun, and slowly, Taegun's violent obsession starts to show.
"If love between a mermaid and a human is not sincere, the mermaid will disappear into the seafoam."
As Haeseo's doubt of Taegun's affection grows, he realizes the curse that has befallen him.