Let's be real for a second. When we talk about the villains in All of Us Are Dead, everyone immediately points fingers at Gwi-nam. It makes sense. He’s a literal unkillable bully with a god complex. But if you really sit back and think about the psychological wreckage left behind in the Hyosan High disaster, Cheol-su in All of Us Are Dead is the one who genuinely gets under your skin. He isn't a zombie. He isn't a "halfbie." He’s just a guy who makes a series of devastating, selfish choices that lead to more deaths than some of the actual monsters.
Kim Cheol-su, played by actor Ahn Ji-ho, represents a very specific, dark corner of human nature. He’s the bystander. He’s the victim who, when given a tiny scrap of power, uses it to pull the ladder up behind him. Honestly, his character arc is one of the most frustrating things to watch in the entire series because it feels so grounded in reality. While the other kids are fighting for their lives with mop handles and archery bows, Cheol-su is busy locking doors.
The Rooftop Betrayal: Why Everyone Hates Cheol-su
The moment that defines Cheol-su happens on the rooftop. It's the turning point for the Hyosan survivors. Our main group—Cheong-san, On-jo, and the rest—are desperately trying to reach the roof to be rescued by the military helicopters. They’ve gone through hell to get there. They’ve lost friends. They’ve watched people turn.
Cheol-su is already up there. He’s safe. He’s alone with Eun-ji for a while, but eventually, he’s the one holding the door. When he hears his classmates screaming and banging on the other side, begging for help, he does the unthinkable. He stays quiet. He doesn't open the door.
Why?
It’s not just cowardice. It’s resentment. Cheol-su was a victim of intense bullying before the outbreak. In his mind, those kids on the other side of the door are part of the system that failed him. He’s not just saving himself; he’s enacting a passive-aggressive form of revenge. By doing nothing, he becomes a killer. It’s a chilling reminder that trauma doesn't always make people heroes; sometimes, it just makes them cold.
When the rescue helicopter arrives, Cheol-su gets on. He tells the soldiers there’s no one else left. He looks them in the eye and lies. That single lie effectively signs the death warrant for the remaining students. If you’ve ever wondered why the military abandoned the school, look no further than Cheol-su’s testimony.
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Is Cheol-su a Villain or Just a Broken Kid?
Categorizing Cheol-su in All of Us Are Dead is tricky. He doesn't have the "cool" antagonist vibes that Gwi-nam has. He’s pathetic. But that’s what makes him so effective as a character. Director Lee Jue-kyu and writer Chun Sung-il didn’t want every villain to be a super-powered zombie. They needed a character to represent the "silent majority" who let bad things happen.
Critics and fans often debate if we should pity him. After all, the school failed him long before the virus did. He was suicidal. He was tormented. But the show draws a very sharp line between Eun-ji and Cheol-su.
- Eun-ji reacts to her abuse with burning, destructive rage.
- Cheol-su reacts with a quiet, selfish apathy.
He had the chance to be better than the people who hurt him. Instead, he chose to be the final nail in their coffin. Honestly, that makes him a more realistic villain than the guy who can jump off buildings and survive. We’ve all met a Cheol-su—someone who thinks their own pain justifies hurting others.
The Military Quarantine and the Final Fate of Cheol-su
Once Cheol-su makes it to the quarantine camp, things don't exactly go well for him. You’d think he’d feel relief, right? But the guilt—or perhaps just the sheer weight of what he did—starts to settle in. In the camp, he’s a ghost. He’s surrounded by people who are grieving, and he’s the one carrying the secret that he left his "friends" to rot.
His interaction with the military is a key piece of the plot's larger commentary on institutional failure. The soldiers believe him because he’s a "clean" survivor. They trust the victim. It’s a bit of meta-commentary: the system only cares about the people who look the part.
Interestingly, Cheol-su’s story doesn’t end with a heroic sacrifice. It ends with him being a footnote in the tragedy of Hyosan. He survives the initial outbreak, sure. But at what cost? He lost his humanity long before most of the characters lost their lives.
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What Most People Get Wrong About Cheol-su’s Motivation
There’s a common theory that Cheol-su didn’t open the door because he was genuinely terrified of the zombies. People say, "Hey, if you were a scared kid and heard scratching at the door, would you open it?"
That’s a fair point, but it ignores the context. Cheol-su knew it was them. He heard their voices. He knew Cheong-san and Su-hyeok. The show makes it clear that his decision wasn't based on a "zombie or human" confusion. It was a conscious choice to prioritize his safety and his spite over the lives of a dozen people.
Another misconception is that he and Eun-ji were "in it together." Not really. Eun-ji was driven by a need to destroy the evidence of her shame (the video). Cheol-su was just trying to disappear. He’s a follower, even in his villainy. When Eun-ji eventually turns into a halfbie and starts her rampage, Cheol-su is just... there. He’s a witness to everything and a participant in nothing.
The Actor Behind the Character: Ahn Ji-ho
We have to give credit to Ahn Ji-ho. Playing a character this disliked is a tough gig. He managed to make Cheol-su look small, trembling, and physically overwhelmed, which makes the betrayal feel even more visceral. It’s easy to hate a monster; it’s harder to deal with the discomfort of hating someone who looks like they need a hug.
Ahn Ji-ho has been in other notable projects like The Boy Who Had Horns and Nobody Knows, but his role as Cheol-su in All of Us Are Dead is likely what he’ll be remembered for by international audiences. He captured that specific "incel-adjacent" energy of a young man who feels the world owes him something because he’s suffered.
The Ripple Effect of Cheol-su’s Actions
If Cheol-su had opened that door, the entire second half of the season would have changed.
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- The group would have been rescued by the first helicopter.
- The military wouldn't have lost faith in the students' survival.
- Characters like Wu-jin and Cheong-san might have actually made it out alive.
Basically, the "bad" ending for many of our favorite characters can be traced directly back to that one moment on the roof. It’s a classic butterfly effect. One coward’s choice led to a massacre in the forest and the eventual bombing of the city.
The show uses Cheol-su to ask a brutal question: Is survival worth it if you have to become a monster to achieve it? Not a physical monster, but a moral one. By the time the credits roll on Season 1, Cheol-su is one of the "winners" in the sense that he’s breathing. But he’s also the most pathetic figure in the entire narrative.
Why This Matters for Season 2
While we don't have all the details for Season 2 yet, the legacy of the "survivors" in the camp is going to be a major theme. If the truth about the rooftop ever comes out, Cheol-su (if he's still around) will have a lot to answer for. The social dynamic between the students who fought and the students who hid will be a powder keg.
In a world where halfbies like Nam-ra exist—people who are literally part monster but keep their humanity—a "pure" human like Cheol-su who gave up his humanity is a fascinating foil. It flips the script on what it means to be a "monster."
Next Steps for Fans
To truly understand the weight of Cheol-su’s impact on the story, you should do a "villain-focus" rewatch of Episodes 9 and 10. Pay close attention to his facial expressions when he hears the banging on the door. It isn't just fear; it's a grim sort of satisfaction.
If you're interested in how the show compares to the original Webtoon, you'll find that Cheol-su's character is expanded significantly in the Netflix adaptation to provide this exact moral conflict. Keep an eye on the official Netflix social channels for Season 2 casting updates, as the fate of the quarantine camp survivors will likely be the first thing addressed in the new episodes.
Check the "making of" specials on Netflix as well; the creators discuss how they intentionally built the rooftop set to feel claustrophobic, heightening the tension of Cheol-su's choice. Understanding his background as a victim of school violence is key to seeing the show not just as a zombie flick, but as a scathing critique of the South Korean education system and its failures to protect the vulnerable.