Forbidden encounter: Captain Xie Chuchen of the Naval Special Forces rescued the mysterious mermaid Yunwen during a sea mission and hid him in a private bay against military orders. Two completely different worlds began to intertwine.
Dangerous curiosity: Yun Wen is full of curiosity but distrustful of the human world. Xie Panchen is attracted by his innocence and mystery that are different from ordinary people. The two gradually develop subtle emotions as they get along day and night.
Identity crisis: Xie Panchen's boss Zhao Zhiyuan begins to doubt his secret. At the same time, marine biologist Professor Lin discovers evidence of the existence of mermaids, threatening Yunwen's safety.
Forced separation: The military raided Xie Chuchen's residence and took Yunwen away. Xie Chuchen did not hesitate to disobey military orders to save him, and faced the danger of military trial.
Secrets of the Deep Sea: Yunwen is taken to a secret research base and discovers that the military plans to use the mermaid tribe for military experiments. He must decide whether to trust humans to save his own people.
Concept: the agreement between ocean and land