‘S LINE’ – The Dark Thriller That’s Breaking Internet and Winning at Cannes

S LINE introduces a world where the unthinkable becomes visible: red threads floating above people’s heads that reveal their sexual connections. Hyeon Heup, played by Arin, is born with a rare curse—she can see these mysterious S Lines, and she believes this gift brings disaster to everyone around her.​​

When a series of brutal murders rocks her neighborhood, she discovers someone else has unlocked the ability to see S Lines through mysterious glasses. Her childhood friend falls into a coma after using the glasses, forcing Hyeon Heup to team up with Detective Han Ji Uk (Lee Soo Hyuk) to uncover the truth.​​

As their investigation deepens, the stakes grow deadlier. Those around them suffer inexplicably. The glasses’ creator emerges from the shadows, orchestrating an elaborate trap. Trust becomes dangerous. Truth becomes fragile. And the question becomes clear: What would society look like if everyone’s most private moments were exposed for all to see?​

Meet the Cast: Powerhouse Performances That’ll Leave You Stunned

Lee Soo Hyuk transforms into Detective Han Ji Uk

—a charismatic investigator simultaneously chasing the S Line mystery and a murder case. With an alarming number of red lines above his head, Ji Uk’s complicated past collides with his pursuit of justice.​​

Arin, member of K-pop sensation OH MY GIRL, makes a dramatic acting pivot as Shin Hyeon Heup, a reclusive student dealing with serious psychological trauma.

Playing a character where “loneliness and strength coexist,” Arin delivers a transformative performance, even cutting her hair short for the role.​

Lee Da Hee plays Gyu Jin, a high school teacher who appears warm and quirky on the surface—but hides an unfathomable inner world.

Despite her attractive appearance, she has no S Lines at all, making her the most mysterious character in the drama.​​

Lee Eun Saem completes the ensemble, adding depth to this twisted narrative.​

Why S LINE Is Not Your Average K-Drama Thriller

This isn’t a standard murder mystery. S LINE is a provocative societal experiment exploring sexual shame, surveillance paranoia, and how fragile human society truly is. Director Ahn Joo Young, making her drama debut after a successful film career, deliberately reinterpreted the webtoon’s concept—in her version, only some people can see the S Line, hinting at a differentiated worldview.​

Critics are calling it “freaking viewers out with its dark take,” and for good reason. The drama digs deep into uncomfortable themes: What happens when boundaries are stepped on? How fast can reputations shatter? What does privacy mean in a world of total exposure?​

What Viewers and Critics Are Saying

“S LINE completely broke the typical K-drama formula. This is bold, provocative, and genuinely terrifying.”​

“As a psychological thriller, it’s a societal experiment playing out on screen. The lines aren’t just visual gimmicks—they’re psychological triggers.”​

“The cast delivers incredibly strong performances. The gloomy tone and raw look at hypocrisy we live with makes this unmissable.”​

“This drama is freaking me out—and I can’t stop watching. It’s one of the best Korean thrillers of 2025.”​

Your Questions, We Answer

Q: What makes S LINE different from other Korean thrillers?

A: Unlike typical mystery dramas, S LINE tackles privacy invasion and sexual shame head-on. It’s a dark fantasy blended with psychological thriller elements—exploring what happens when society’s most private secrets become public.​

Q: Is this drama R18+ for a reason?

A: Yes. The drama deals with mature themes including sexual relationships, violence, and psychological trauma. It’s designed for adult audiences who can handle provocative, uncomfortable storytelling.​

Q: Do I need to watch this if I’m not into thriller dramas?

A: If you love best Korean thriller dramas or appreciate psychological depth, absolutely. S LINE isn’t just suspense—it’s a commentary on human nature and societal fragility.​

Q: How many episodes are there?

A: All 6 episodes are now available on Viu, each running approximately 50-56 minutes. Perfect for a complete binge experience.​

Q: Why is it a big deal that S LINE went to Cannes?

A: S LINE became the only Korean drama invited to the 8th Cannes International Series Festival, competing against top international productions. The drama won the Best Music Award, marking a historic moment for Korean television.​

Q: What’s the episode release schedule on Viu?

A: All episodes are now live on Viu! You can watch from Episode 1 through Episode 6 consecutively without waiting.​

Episode Guide – A Journey Into Darkness

Episode 1: The Girl With the Sunglasses

– Hyeon Heup’s curse is revealed as she tracks a mysterious killer through her neighborhood.​

Episode 2: The Animal Kingdom

– Hyeon Heup reconnects with Seon A at Bangju High School, where mysterious glasses appear and danger escalates.​

Episode 3: The Apartment

– Ji Uk investigates Seon A’s fall from the school rooftop, revealing an English teacher’s shattered world.​

Episode 4: Miseong Motel

– A school employee named Mi Seong discovers the S Line glasses and becomes consumed by jealousy.​

Episode 5: The Glasses

– Ji Uk finally discovers the glasses in a blood-filled bathtub and accepts the horrifying truth.​

Episode 6: Chaos on the Horizon

– As Hyeon Heup approaches a pivotal birthday, a shocking revelation about Seon A’s S Line changes everything.​

Ready for the Most Provocative Thriller of 2025? Stream S LINE on Viu Now

Don’t miss the Korean drama that’s breaking internet discussions worldwide. S LINE challenges everything you believe about privacy, relationships, and human nature. Stream all 6 episodes exclusively on Viu—available in English and Chinese subtitles.​