The Legend of the Blue Sea — Characters & Cast

Driven by pure, unyielding love for Joon-jae/Dam-ryeong and a desire to belong in his world.

Begins as a clueless mermaid struggling with basic human customs. As she navigates Seoul, she evolves into a fierce protector who risks her life to shield Joon-jae, ultimately enduring physical injury and ocean healing before returning as a mature, confident partner.

Initially money and finding his long-lost mother; shifts to protecting Shim Cheong and preventing their past tragedy from recurring.

Starts as a cynical, materialistic con artist who uses hypnotism to scam corrupt wealthy targets while nursing trauma from his mother's abandonment. Through Cheong's unconditional devotion and past-life visions, he evolves into an empathetic, self-sacrificing legal prosecutor determined to protect those he loves.

Wealth and personal survival, evolving into genuine loyalty to his found family.

Joon-jae's senior con-partner. Initially motivated strictly by profit, he discovers Cheong's mermaid identity and briefly considers selling her. Ultimately, his bond with Joon-jae wins out, and he serves as a loyal ally in bringing down the villains.

Validation and parental affection, which mutates into toxic jealousy toward Joon-jae.

Introduced as Joon-jae’s polite, quiet stepbrother who seeks his stepfather’s approval. As he realizes his stepfather will never truly love him and under his villainous mother's influence, he spirals into envy and rage, becoming a lethal antagonist.

Greed, self-preservation, and murderous obsession.

Reincarnated from Lord Yang (the Joseon nobleman who hunted Se-hwa) into an escaped convict and hitman hired by Joon-jae's stepmother. He relentlessly pursues Joon-jae and Cheong across both eras until his past memories drive him insane.