She has super strength and the ability to read and erase one's memory.
A mermaid in the Joseon era who fell in love with Dam-ryeong as a child after saving him. As they are initially unable to stay together due to his arranged marriage and Se-hwa's inability to turn her tail into legs without reaching adulthood yet, she erases his memories. The two meet again and suffer a tragic fate together, beginning the first omen that will tie into their reincarnations.
In the modern-day, she arrives in Seoul to follow Joon-jae after having fallen in love with him. He names her Shim Cheong, which means 'stupid' as she is highly ignorant about common things up on land. Like her past self, she has super strength and the ability to read and erase one's memory.