During a visit to a swimming pool, ordinary South Korean high schooler Haein is unexpectedly pulled into a whirlpool, leading to her unconsciousness. Upon awakening, she discovers herself in the depths of the ocean, where she encounters Ellime claiming to be her father. Haein's world is turned upside down as she unravels the truth about her origins, being the offspring of the Spirit King and a half-elf mother. Now faced with a new reality, can she navigate the challenges of this unfamiliar world and survive the trials ahead?