You’ve probably seen a dozen serial killer movies this year. They usually follow the same rhythm: a grizzled detective, a trail of bodies, and a cat-and-mouse game that ends in a rainy alleyway. But Won Shin-yun’s 2017 thriller flipped the script by giving us a killer who can’t even remember his own crimes. It's a brutal, disorienting ride. What really keeps the tension high, though, isn't just the memory loss gimmick—it's the Memoir of a Murderer cast.
The performances here aren't just "good." They’re visceral.
When you look at the lineup, you see actors who didn't just show up to read lines; they underwent massive physical transformations. Sul Kyung-gu, for instance, lost a terrifying amount of weight to play Byung-su. It wasn't just about looking thin. He wanted to look hollowed out. Like a man whose mind was literally evaporating.
The Haunting Lead: Sul Kyung-gu as Kim Byung-su
Sul Kyung-gu is basically royalty in South Korean cinema. If you've seen Peppermint Candy or Oasis, you know he doesn't do "half-way." In this film, he plays Byung-su, a retired serial killer suffering from Alzheimer’s.
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Byung-su is a complicated guy. You aren't supposed to like him—he’s a murderer, after all—but the way Sul plays him makes you feel a weird, uncomfortable empathy. He’s a man trapped in a decaying body, trying to protect his daughter from a new killer who might be real or might just be a hallucination. Honestly, the facial twitches Sul does in the film? Those weren't just random. He practiced those to mimic the neurological degradation of dementia. It’s some of the most committed acting you’ll ever see in a genre film.
He lost nearly 20 pounds for the role. In a movie where the protagonist is unreliable, the actor has to be the anchor. Sul Kyung-gu is that anchor. He makes you believe in Byung-su’s confusion, even when the plot starts twisting into knots.
Kim Nam-gil: The Chilling Contrast
Every hero—or anti-hero—needs a foil. That’s where Kim Nam-gil comes in as Min Tae-joo.
On the surface, Tae-joo is the perfect son-in-law candidate. He’s a police officer. He’s polite. He’s handsome. But Kim Nam-gil plays him with this eerie, glassy-eyed stillness that makes your skin crawl. There’s a specific scene where he smiles at Byung-su, and you can see the mask slip just for a millisecond.
Kim Nam-gil is often known for more "dashing" roles in K-dramas, so seeing him go full-tilt into this sociopathic territory was a shock for a lot of fans. He didn't play a cartoon villain. He played a man who knows exactly how to manipulate a senior citizen with a failing brain. The chemistry between him and Sul Kyung-gu is electric because it’s built on mutual suspicion. It’s a literal battle of wits where one person is losing theirs.
Seolhyun and the Stakes of the Story
Kim Seol-hyun, often just known as Seolhyun from the K-pop group AOA, plays Eun-hee, Byung-su’s daughter.
Look, idol-actors often get a lot of flak. People assume they’re just there for the marketing. But Seolhyun actually holds her own here. Eun-hee is the emotional core of the film. Without her, Byung-su is just a crazy old man. Because she exists, his struggle has weight. She’s the only reason he’s fighting to keep his memories together.
She has to play a very specific kind of frustration: the daughter of someone who is slipping away. It’s a thankless job in a movie full of flashy killer performances, but she brings a necessary groundedness. If she didn't feel real, the stakes wouldn't feel high.
The Supporting Players Who Round Out the World
You can’t talk about the Memoir of a Murderer cast without mentioning Oh Dal-su.
He plays Byeong-man, a local cop and Byung-su’s long-time friend. Oh Dal-su is one of those character actors you see in everything from Oldboy to The Host. He provides the only bit of levity in an otherwise pitch-black movie. His presence reminds us that Byung-su had a life outside of his dark past.
Then there’s Hwang Seok-jeong as Jo Yeon-joo. She’s fantastic. Her role adds another layer of tension to Byung-su’s daily life, acting as a bridge between his mundane reality and the encroaching chaos of his mind.
Director Won Shin-yun’s Vision for the Cast
Director Won Shin-yun didn't want this to be a standard adaptation of Kim Young-ha’s novel. The book is very internal. To make it work on screen, he needed actors who could project internal thoughts through physical action.
He pushed the cast to be gritty. There’s a lot of mud. There’s a lot of cold. Most of the filming took place in harsh conditions to reflect the "winter" of Byung-su’s life. When you see the actors shivering or looking genuinely exhausted, it’s usually because they were. This isn't a "pretty" movie. It’s a movie about the rot of the soul and the brain.
Why the "Director’s Cut" Changes Everything
If you’ve only seen the theatrical version, you’re missing half the story. The Memoir of a Murderer cast actually filmed two slightly different versions of the narrative.
The Director's Cut (often titled Another Memory) significantly changes the ending and the character motivations. It makes Kim Nam-gil’s character even more ambiguous and Sul Kyung-gu’s character even more tragic. If you want to see the full range of what these actors did, you have to track down the extended version. It changes the way you view the entire cast's performances.
A Masterclass in Genre Acting
What makes this ensemble work is that they don't treat it like a "slasher" flick. They treat it like a Greek tragedy.
Byung-su isn't just running from a killer; he’s running from time. Tae-joo isn't just a murderer; he’s a reflection of Byung-su’s younger, more efficient self. The way the actors play off this "generational" mirror is fascinating. You see the old lion trying to fend off the young hyena, but the old lion can’t remember where he put his claws.
Practical Takeaways for Fans of the Film
If you're looking to dive deeper into the work of this cast, or if you're trying to understand why this movie specifically stands out in the crowded South Korean thriller market, keep these points in mind:
- Watch Sul Kyung-gu in "Public Enemy" right after this. The contrast between his role as a relentless detective and his role as a fading killer in Memoir of a Murderer shows his incredible range.
- Compare the two versions. The theatrical cut is a solid thriller. The Director’s Cut is a psychological mind-bender. The cast's performance in the final 20 minutes of the Director's Cut is much more nuanced.
- Pay attention to the eyes. In South Korean cinema, "eye acting" is a big deal. Watch how Kim Nam-gil uses his gaze to intimidate versus how Sul Kyung-gu uses his to show confusion. It’s a masterclass in non-verbal storytelling.
- Look for the symbolism in the costumes. Notice how Eun-hee’s clothes are always bright compared to the muted, earthy tones of Byung-su and Tae-joo. It’s a visual representation of her innocence being caught between two dark forces.
The Memoir of a Murderer cast succeeded because they committed to the ugliness of the story. They didn't try to be likable. They tried to be real. In a world of sanitized, predictable thrillers, that's exactly why this movie still gets talked about years later.
To fully appreciate the craftsmanship, your next step should be a back-to-back viewing of the two different cuts. Start with the theatrical version to get the plot down, then watch the Director’s Cut to see how a few different acting choices and editing tweaks can completely reframe a character's morality. It is a rare opportunity to see how much power an actor has over the narrative arc of a film.