When Hae-Seo sees Tae-Gon, the boy he once saved, return to the sea where he lives as an adult, he feels both joy and a deep attraction toward him. Though they reunite in human form, he accidentally reveals his true identity as a mermaid to Tae-Gon, and he begins to show increasingly violent and obsessive behavior toward him...

“The love between a mermaid and a human will turn to bubbles if it isn't true love.”

Having begun to doubt Tae-Gon’s affection, Hae-Seo realizes he has been cursed.

(Source: MrBlue, translated)