Good start, terrible ending
S Line is a dark and gripping mini-series that combines mystery, psychological tension, and social commentary in a unique and disturbing way.The story follows a girl who can see red lines above people's heads, revealing their sexual relationships. For others, the line is visible only if they wear some random glasses.
Each episode follows a different case where someone gets the glasses and their life takes a dramatic turn. What starts as curiosity often ends in tragedy, and the deeper the story went, the more disturbing it became.
The pacing was slow but reasonable. With only 6 episodes, the story was building effectively, however out of nowhere, the final episode takes a whole different path and the series ends up disastrously without giving a proper explanation of glasses, the girl's ability to see the red lines or the supposedly cult that was seen in the final episode. The show could have been so good, but the finale made it into a disappointing affair eventually.
Overall, S Line is a wasted potential, that had a great story, but went wrong due to it's confusing and unexplainable ending.
My Rating : 2.5/5
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A Red Thread You Won’t Forget
I really enjoyed watching S Line. It’s a fresh, daring take on privacy and human connection wrapped in a dark thriller. The core concept is striking: people’s past sexual partners appear as glowing red lines above their heads, visible through special glasses. The show uses this premise to explore how society reacts when intimacy is suddenly public, and how obsession and judgment spiral into violence.Hyun-heup (played by A Rin), who can naturally see these red lines without glasses, offers a unique perspective. Lee Soo-hyuk’s Han Ji-wook, a calm and emotionally restrained detective, grounds the narrative as the chaos intensifies. The production is visually compelling, especially with the symbolic use of the red lines and a haunting soundtrack that builds suspense throughout.
That said, the series struggles with pacing, especially from Episode 3 onwards. The suspense and momentum dip noticeably, and I found myself watching at 1.5x speed just to maintain the thriller’s intensity. This mid-series slowdown makes the story feel uneven, even though the tension returns toward the end.
One common criticism I’ve seen is disbelief that so many people in the story would resort to murder over the red lines. But in the show, it’s clear that the violence isn’t a spontaneous societal breakdown. It happens because Lee Da-hee’s character is handing these glasses to people who are already unstable or dangerous—those who would kill to protect their secrets or gain control. This explains the high death toll and violent conflicts, making it a story less about universal chaos and more about how dangerous tools fall into dangerous hands.
The finale divides viewers. Some felt it shifted too suddenly toward a dystopian, almost cult-like tone, which didn’t sit well with the build-up. This tonal shift felt jarring and left some narrative threads unresolved, leaving fans frustrated. It also felt like the final episode was less about wrapping up the story and more about setting up a possible second season.
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Refreshing storyline that missing proper screenwriting and directing.
The storyline was very interesting and refreshing, but I wish they put more effort into the storytelling. It would be great if they spent more time developing the characters and showing their background and the story of the chases; they could spend more time on it as well. It's a shame as I quite liked it, but it was missing the depth, and also some scenes in the last episode were just all over the place. It would be better if they added more episodes and made a proper drama.Was this review helpful to you?
Brilliant Concept, Great Start - Ending "demands" S2
When this drama was first announced, I was instantly intrigued by its bold, original concept - the idea of physically seeing someone's "S-Line" was like a marker of power or influence had so much potential. And the show starts strong. Each episode adds new layers through intriguing characters and mysterious events, all while staying rooted in the core story of Sin Hyeon Hop (Arin) and Detective Han Ji Uk (Lee Soo Hyuk), as they unravel the truth behind the S-Line phenomenon.What really stood out was the way each episode tackled a new case, all connected by a subtle thread of social commentary. The ability to see someone’s S-Line felt symbolic—representing privilege, leverage, and the consequences of having access to hidden truths. It raises an interesting moral question for the viewer: if such a thing existed in real life, would it lead to progress or pure chaos?
Up until Episode 5, the show delivers on all fronts: mystery, pacing, acting, music. But unfortunately, Episode 6 stumbles just when answers are most needed. The supernatural twist isn't properly explained, leaving too many loose ends: Who/What is the creator of S-Line and the glasses? What’s the true motive? Instead of answers, we’re left with speculation.
That said, the short format, strong performances, and thought-provoking premise make S-Line worth watching ONLY IF a Season 2 is confirmed. As a standalone, it’s frustratingly incomplete, but with a continuation, it has the potential to become a truly standout series.
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I hope there will be a season two
The ending was super open to interpretation but I didn’t really get the ending — it was way too abstract for me.Was this review helpful to you?
A dark, daring exploration of shame, surveillance and sexual privacy
S-Line is not your average K-drama. In just six tightly packed episodes, it dives headfirst into some of the most uncomfortable truths of modern society—sexual double standards, shame, and the cost of visibility in a hyperconnected world.
Set in a near-future Seoul, the series introduces a surreal yet eerily familiar concept: invisible red lines, or “S-Lines,” appear above people’s heads to indicate who they've had sexual relations with. For some, it's a web of tangled connections. For others, it’s a scarlet letter. And for those who can see these lines, life becomes a twisted game of secrets, power, and exposure.
But S-Line doesn’t exist to shock for shock’s sake. It doesn’t glorify public access to private lives—instead, it interrogates it. The lines are a metaphor for how society already peers into people’s personal choices, particularly women’s, and uses them as grounds for judgment, exclusion, or even violence. It's not about whether someone deserves to be seen—it’s about how dangerous a world becomes when everyone’s sexual history is visible, but no one cares about the context.
The performances are stellar—Arin delivers a surprisingly nuanced portrayal of a teenager burdened with a vision no one else has, while Lee Soo-hyuk anchors the mystery with tortured charisma as a detective whose own lines come back to haunt him. Lee Da-hee’s character adds a layer of eerie calm to the story, reminding us that silence can hide deep chaos.
I highly recommend this drama to anyone interested in a kdrama without a regular and predictable storyline.
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Yes, Korea!
What I thought of the series: Yes, Korea! I like mystery TV series and this one ended up high on the list.Then the fact that Lee Soo Hyuk has one of the main roles is a big plus. This is probably my third series but him. He is so good!
#leesoohyuk
You can find more of my reviews on Instagram. :D See my homepage about my Instagram account. Some of my reviews are under five hundred words so I can't post them here. (*^▽^)/★*☆♪(*^-゜)vThanks!
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Don’t waste your time
You want to know how trash it is?It give the vibe of the drama called “Somebody”
But it is AS WORSE as “Love Alarm”.
The ending was a mess and honestly the concept had so much potential but they COMPLETELY wasted it and were successful on making something with potential a trash…
Really do not recommend
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This review may contain spoilers
Unique, Stylish, Bold, and Thought-Provoking
I decided to watch this because I am an avid fan of Lee Soo-hyuk. He has a knack for choosing very eccentric dramas, and I find that very intriguing about him. The central concept of S Line is a surreal and terrifying phenomenon: the sudden appearance of glowing red lines, or S-Lines, above people's heads. These lines are not just any visual gimmick; they represent a public record of an individual's past sexual relationships, connecting them to every person they've been intimate with, chaotic to say the least. The story unfolds as a mysterious murder mystery, triggered by the chaos that erupts when these private connections are suddenly made public. The show follows three main characters whose lives become intertwined with the S-Line phenomenon.The three main characters, or should I say driving force, in this drama are Detective Han Ji-wook (Lee Soo-hyuk), assigned to a bizarre death case tied to the S-Lines. He initially dismisses the phenomenon as an urban legend. Still, after acquiring a special pair of glasses that allows him to see the lines, he is shocked to discover a tangled web of connections above his own head. This discovery forces him to confront his past and dive deep into the mystery. Shin Hyun-heup (Arin), a high school student, is the only person who has been able to see the S-Lines since birth. She has lived a reclusive life, burdened by this curse-like ability and the tragic family secret it exposed. She becomes a key figure in the investigation, as her unique perspective is crucial to understanding the phenomenon. Lee Gyu-jin (Lee Da-hee) is a mysterious high school teacher who appears calm and collected on the surface but harbors dark secrets. She is a central antagonist, revealed to be behind many disturbing events and using her own ability to see the S-Lines to manipulate others and orchestrate a twisted plan.
As the series progresses, the plot delves into a murder investigation, a shocking family tragedy, and a commentary on how society would react if all intimate secrets were laid bare. The finale culminates in a climactic confrontation where the S-Lines, once only visible to a select few, become visible to everyone, plunging the world into a state of chaos and forcing humanity to grapple with radical honesty. The ending is both haunting and thought-provoking, leaving a wide-open ending for a potential second season.
Taking a deep dive into the characters, I have to say that as complex as S Line is as a story, as fascinating is the cast of S Line for their praiseworthy performances, particularly in how they each handle their roles within the bigger scheme of the drama's dark and multifaceted themes.
Lee Soo-hyuk as Han Ji-wook brings his signature charismatic and icy elegance to the role of a detective grappling with a personal and professional crisis. His portrayal of a man whose own secrets are exposed is layered and compelling.
Arin, as Shin Hyun-heup, is the surprise for me in her dramatic transformation from her bubbly idol image as a member of the K-pop group Oh My Girl. She delivers a nuanced and emotional performance as a young adult burdened by a profound psychological trauma. Her character is the emotional anchor of the story, representing the vulnerability of those who cannot hide their past.
Lee Da-hee as Lee Gyu-jin is the outlier for me in that I didn't recognize Lee Gyu-jin as Lee Da-hee until the last episode. She was quite enchanting in her portrayal of the mysterious and manipulative high school teacher. Her performance is chilling and captivating, as she embodies a character who believes she is cleansing the world by exposing secrets.
I am not at all surprised that S Line received a mixed but generally positive reception or that reviewers and viewers alike admired the show for its innovative and daring premises and ability to use a fantastical concept as a potent metaphor for real-world issues, such as online surveillance, cancel culture, and the double standards of sexual shame. I also think it's fast-paced, and a six-episode format is one of its biggest strengths as it prevents the story from dragging and keeps me engaged and on the edge of my seat. The cinematography is also admirable for its use of dark, eerie visuals that complement the psychological thriller genre. I am not surprised at all that it won the Best Music award at the Cannes International Series Festival, highlighting its strong production value.
This drama is not for everyone, and I may be among the very few who gave it a 10-star rating, but that is okay. Not everything is for everybody. I enjoyed it for its uniqueness, style, boldness, and thought-provoking nature, particularly in how it challenges conventional K-drama storytelling. It is a must-watch for fans of psychological thrillers, and if you are looking for something outside the norm.
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When Ambition Turns into Absurdity. The Worst Content I’ve Ever Seen—And I’ve Seen a Lot
An absurd series at its best. The creators clearly tried to be smart and unique with the concept—like an artsy, thought-provoking series—but it ended up becoming a pathetic joke. While the concept is appreciable, the story is all over the place, lacking any clear vision. Honestly, I’ve never seen such terrible content in my life.Was this review helpful to you?
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Red and Crimson World
The latest episode of Sline is a banger, folks!! The mystery underlying the city where glasses let out a craving for power, but the consequences lead to deep remorse. Han Ji Uk and Sin Hyeon Hop discover a deep mystery with these glasses, which give the weak a surge of power but later become a black hole of sorrow and guilt, leading them to a cult of greed.Episode 5, titled Glasses, and Episode 6, Cafe Byon/S-line Alpha, have an intertwined connection. In episode 5, now that the glasses are with Ji Uk, he tries to get into the details about these glasses—the lines that appear and how they become the cause of someone’s comfort and greed. A high school girl comes up to the station to file a complaint against the boys who drugged her and left her unconscious. The case with a trainee idol and his group of friends makes it a cool game to exploit the girl’s modesty, yet they have no remorse. The case gets even more tangled when a line on Seon Ah somehow aligns with someone close to them.
Episode 6 opens on a nice note where Sin Hyeon Hyeop starts to feel love for Jun Seon, and on the other hand, another girl is targeted for fun. A college student finds herself in a scandal where her private moments are captured by a student and are now being shared with her. Teacher Gyu Jin meets her and gives her a pair of glasses to fulfill her revenge.
Gyu Jin appears with a sadistic look and manipulates Ji Uk to kill his father. Instead, he attacks Gyu but is taken under her spell. In the meantime, her friends, too, are under the spell of the glasses. Hyeon saves her in time and enters the same realm as the detective. Gyu welcomes her to the cult and their motive to kill all those with sins and paint the town crimson. Her curse will no longer be hers.
Time passes, and Seon comes out of the coma. She, too, sees red lines without those glasses, and so does everyone. Towards the end, Gyu makes sure never to lose sight of her, but is the game over for her?
Read Full review on- https://goodhappiness4.wordpress.com/2025/07/25/a-cult-in-crimson-sline-paints-a-blood-red-world-for-all-episode-5-6-review/
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Red Lines Reveal Dark Secrets
If Strangers from Hell and Taxi Driver had a child — it would be S-Line.While the main plot of S-Line isn’t exactly the same as those dramas, it feels similar. The overall vibe is heavy, tense, and unsettling, much like Strangers from Hell. There’s a constant sense of discomfort and mystery that keeps you on edge the entire time.
In terms of structure, it follows a more episodic format, similar to Taxi Driver. The core storyline develops slowly in the background while new plots and mini-stories unfold in each episode. This keeps the drama fresh and engaging, giving you something new to latch onto every time while still weaving in deeper threads (no pun intended).
The leads do a great job portraying subtle shifts in emotion, and the supporting characters are equally unsettling. They are layered and unpredictable, you never quite know who to trust. I’ve always loved Lee Soo Hyuk and rarely see him in lead roles, so it was such a treat to see more of him on screen (and he absolutely delivered!). As for Lee Da Hee, while I haven’t always connected with her performances in the past, she had a much smaller role in this and actually suited it really well - I was pleasantly surprised. A Rin played her character so well, it was interesting to see a different side of her acting.
The storytelling is bold (sometimes disturbing) and while it’s not perfect, with some parts feeling underdeveloped, the plot is intriguing and easy to binge. It’s fast paced with a unique concept, and despite only 6 episodes, the drama uses its time well to thoughtfully uncover many details.
If you like psychologically heavy dramas with a mysterious edge and enjoy watching dark stories unfold one episode at a time, S-Line is absolutely worth checking out!
TRIGGER WARNING: some graphic scenes and sensitive themes like suicide are featured throughout.
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