If you finished the last episode with doubts or want to understand all the details, check below the complete explanation of The Mermaid's Kiss finale.
Summary of The Mermaid's Kiss finale
The final episode reveals that Do Eun-hyuk is the true serial killer behind all the deaths. Throughout the plot, the character presents himself as a loyal friend of Han Seol-ah, but his obsession hides extremely dangerous behavior.
Among the crimes committed by him are:
- Murder of Seol-ah's ex-boyfriends
- Death of Yun-ji
- Murder of the powerful President Kim
The decisive moment happens when Cha Woo-seok manages to record Eun-hyuk's confession using a smartwatch. The recording allows Seol-ah to discover the entire truth.
During the final confrontation, Seol-ah throws herself in front of a bullet to save Woo-seok — a scene that marks the emotional climax of the series.
The fate of the main characters
Han Seol-ah: The protagonist survives the gunshot and finally discovers that her best friend was responsible for destroying her life. After the events, she abandons her old career and decides to start over. Her new mission is to help traumatized children, showing a path of healing and reframing pain.
Cha Woo-seok: The investigator proves his loyalty and courage until the end. After the case, he becomes Seol-ah's emotional support and keeps his promise to protect her. The relationship between the two stops being an act and becomes something real.
Do Eun-hyuk: Eun-hyuk establishes himself as one of the most disturbing villains in recent K-dramas. After being arrested and confronted by Seol-ah, he completely loses emotional control. Unable to deal with rejection, he commits suicide in prison, ending his cycle of obsession.
President Kim: The character tries to flee justice, but ends up being murdered by Eun-hyuk inside a safe — a symbolic death that reinforces the theme of consequence and justice.
The great revelation: who is the true monster?
One of the greatest strengths of the screenplay is deconstructing the idea of the "protective friend." Throughout the series, Eun-hyuk seems to be someone trustworthy, but gradually reveals his true nature.
He believed that he was "protecting" Seol-ah, that only he was worthy of being by her side, and that any relationship of hers was a threat. This distorted logic transforms the character into a psychological villain, more frightening than any traditional antagonist.
The most shocking plot twist: the fire from the past
If the crimes in the present were already impactful, the drama still reserves an even heavier revelation: Eun-hyuk was responsible for the death of Seol-ah's parents. Years before, he caused a fire in the family's house, ensuring that the protagonist's parents died. The objective was to manipulate her life from the beginning. This detail completely changes the public's perception of the story, reinforcing that the villain was always in control.
Is the ending happy or sad?
Despite the intense dramatic weight, the ending can be considered bittersweet, but positive.
