“Hye-seong,” a boy living on a remote island, meets “Yoon-hae,” a mermaid he met in the sea, and they become each other’s only friends. However, the two soon break up against each other due to Hye-seong’s move. Six years later, Yunhae gains mysterious abilities and returns to Comet. However, many things have changed for Hyesung to spend all his time with Yunhae like he did when he was young. “I’m a different person than you, Yoonhae.” Yoon Hae’s attachment to the comet is slowly spreading into control…