It has been nearly a decade since a mermaid first washed up on the shores of Spain in a green sparkly dress. Honestly, the staying power of Legend of the Blue Sea cast is kind of ridiculous. Usually, Hallyu waves crash and recede, replaced by the next big Netflix hit or a trendy webtoon adaptation. But this show? It lingers. You’ve probably seen the clips on TikTok or Instagram reels—Jun Ji-hyun trying to eat spaghetti with her hands or Lee Min-ho looking effortlessly cool in a pastel sweater.
There is a specific magic that happens when you pair a generational talent like Jun Ji-hyun with a global icon like Lee Min-ho. It wasn't just about the high-budget cinematography or the "fated love" trope that writer Park Ji-eun loves so much. It was the chemistry. Most shows struggle to balance the slapstick comedy of a fish-out-of-water story with the heavy, tragic stakes of a Joseon-era reincarnation drama. This group pulled it off.
The Powerhouse Duo: Jun Ji-hyun and Lee Min-ho
When people talk about the Legend of the Blue Sea cast, they usually start and end with the leads. That’s fair. Jun Ji-hyun (Gianna Jun) was coming off the massive success of My Love from the Star. She is essentially the queen of the "eccentric but lovable" archetype. As Shim Cheong, she had to play a creature who literally didn't know how to be human. It could have been cringey. In the hands of a lesser actress, the wide-eyed innocence would have felt forced. Instead, she made us believe that a mermaid would actually think a tissue box is a magical toy.
Then you have Lee Min-ho. He played Heo Joon-jae, a high-IQ con artist. Before this, Lee was often criticized for playing the same "rich, brooding guy" in every drama, from Boys Over Flowers to The Heirs. This role was different. It allowed him to show range. He was a hypnotist, a nerd, a pilot, and a grieving son. His transformation from a cold-hearted scammer to a guy who buys a mermaid a pair of Manolo Blahniks is the emotional anchor of the series.
The supporting players you probably forgot were this good
We need to talk about the "con-artist trio." While the romance gets the spotlight, the dynamic between Lee Min-ho, Lee Hee-joon, and Shin Won-ho is what gave the show its pulse. Lee Hee-joon played Jo Nam-doo, the "sunbae" conman. He was the pragmatic one. He was the one who kept reminding Joon-jae that they were supposed to be making money, not adopting mythical sea creatures. His performance was subtle because you never quite knew if he was going to betray the lead or stay loyal. That tension is hard to maintain for 20 episodes.
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Shin Won-ho, playing the silent hacker Tae-oh, became an overnight sensation for his "pretty boy" looks and his hilarious crush on Shim Cheong. It’s funny looking back now—he was a member of the K-pop group Cross Gene, and this role solidified him as a legitimate actor in the eyes of many fans.
Why the villainous arc worked
A drama is only as good as its villain. Sung Dong-il is a legend in the industry, often known for playing the warm, grumpy dad in the Reply series. Seeing him as Ma Dae-young was jarring. He was terrifying. The way he moved between the Joseon timeline as the greedy Lord Yang and the modern timeline as a fugitive murderer was masterclass acting.
His presence meant the stakes weren't just "will they get married?" but "will they survive?" The Legend of the Blue Sea cast benefited immensely from having a veteran like him to ground the supernatural elements in real, visceral danger.
Then there’s Hwang Shin-hye and Lee Ji-hoon. The "evil stepmother and stepbrother" trope is a K-drama staple, but Lee Ji-hoon brought a surprising amount of pathos to Heo Chi-hyun. You almost felt bad for him. Almost. He was a victim of his mother’s ambition, and his slow descent into darkness was one of the most well-paced character arcs in the show.
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The cameo culture of the series
Part of what made the casting feel so "prestige" was the sheer number of high-profile cameos. Remember Jo Jung-suk? He appeared as a male mermaid (a merman, technically) working as a 119 paramedic. It was only for a couple of episodes, but his "lesson" to Shim Cheong about how mermaid tears turn into pearls—and how they can be used as currency—was arguably the funniest sequence in the whole drama.
We also saw Krystal Jung as a flight attendant in the first episode, and Kim Seul-gi as a sassy mermaid in the finale. These weren't just random faces; they were established stars willing to show up just to be part of the world created by director Jin Hyuk.
The Joseon Connection: More than just costumes
A lot of viewers get confused by the sageuk (historical) portions of the show. The Legend of the Blue Sea cast had to play double roles, essentially. Lee Min-ho as Kim Dam-ryeong was a completely different vibe from his modern character. He was more stoic, more tragic.
The historical segments were based on a real story from the Eou Yadam, a collection of folk tales from the Joseon period. It’s about a magistrate who returns a captured mermaid to the sea. The show took that tiny grain of truth and built a sprawling epic around it. The transition between the past and present required the actors to maintain a sense of continuity in their "souls" while changing their mannerisms completely.
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Production value and location scouting
You can't talk about the cast without mentioning the backdrop. The early episodes in Palau and Spain set a visual tone that was incredibly lush. When the actors are performing against the architecture of Girona or the turquoise waters of the Pacific, the performances have to be big enough to match the scenery.
The chemistry wasn't just between the people, but between the characters and their environment. When Shim Cheong is wandering through Seoul, the city itself becomes a character. The contrast between the beautiful, lonely sea and the cramped, busy streets of Gangnam serves to highlight the isolation felt by the leads.
The impact on the actors' careers
For Lee Min-ho, this was his last project before his mandatory military enlistment. It was a "mic drop" moment. He left the industry for two years at the absolute top of his game. For Jun Ji-hyun, it proved that she was still the undisputed queen of romantic comedy after having her first child.
But look at the others. Shin Hye-sun, who played the "second lead" Cha Si-ah, went on to become a massive star in her own right with Mr. Queen and Welcome to Samdal-ri. Back then, she was just the annoying rival, but her talent was already peaking. It’s a testament to the casting director's eye that they filled even minor roles with future A-listers.
Actionable Takeaways for K-Drama Fans
If you're looking to dive back into the world of the Legend of the Blue Sea cast, or if you're a first-time viewer, here is how to get the most out of it:
- Watch for the Parallels: Pay close attention to the objects that reappear in both timelines—the jade bracelet, the paintings, the vases. The cast plays these moments with a sense of "déjà vu" that is very subtle.
- Don't Skip the Epilogues: Almost every episode has a "stinger" at the end. These are often the funniest or most revealing moments for the supporting cast.
- Research the Folklore: Look up the Eou Yadam. Knowing that the mermaid story has roots in actual Korean history makes the stakes feel a bit more grounded.
- Follow the Career Trajectories: If you liked Shin Hye-sun or Lee Ji-hoon, check out their later work. This drama was a launching pad for several "second lead" actors who now headline their own shows.
- Focus on the Sound Design: The soundtrack features Lyn and Yoon Mi-rae, but the way the actors interact with the music—especially the "mermaid internal monologue" sounds—is a masterclass in comedic timing.
The show isn't perfect—the plot drags a bit in the middle as they try to figure out the "rules" of the mermaid's heart—but the performances carry it through the slow patches. It remains a essential watch for anyone trying to understand why K-Dramas took over the world. You come for the mermaid, but you stay for the surprisingly deep meditation on fate and the incredible ensemble that brought it to life.