Netflix kept the original webtoon’s stolen-identity setup — then changed almost everything else. Here’s what really happens in Ludovico’s Field Mouse, and why its ending means something very different. Full spoilers.
If you finish Netflix’s Mousetrap and go looking for the original webtoon, you’re in for a surprise.
It starts as the same story. A novelist named Je Moonjae, who hasn’t left his home in years, discovers a man living under his name. His identity is already gone, and everyone around him believes the fake is the real one. Moonjae teams up with Noja, the loan shark who’s owed money by him, to hunt down the Rat.
Go a little deeper and it becomes a completely different story. The Rat in the drama is Seo Yumin; in the webtoon, it’s Oh Gi-wan. In the drama, the first Je Moonjae is Detective Sunyong; in the webtoon, the first Je Moonjae is the Rat himself. And most importantly, the choice Moonjae makes at the end goes in the opposite direction.
This is less an adaptation than two works that started from the same folktale and arrived at different questions.
What the Original Webtoon Actually Is
Ludovico’s Field Mouse began serialization on Daum Webtoon in February 2017 and ran to completion in April 2020. Three-plus years of serialization means it’s not a short read. It’s currently available as a completed work through Kakao Webtoon.
Field Mouse wasn’t Ludovico’s debut. He’d previously serialized works like Interview and Ludovico’s Animated Films, and had a reputation for cinematic staging and twist-driven storytelling. There isn’t solid data to claim Field Mouse was a massive mainstream hit at the time. What’s clear is that it built a devoted following on the strength of its premise, and the fact that Netflix rebuilt it as a ten-episode global series years after it ended says something about its staying power.
The Webtoon’s Moonjae Is a Far Less Likable Man
Where the drama’s Moonjae spent three years indoors because of panic disorder, the webtoon’s Moonjae spent ten. And for a different reason.
He stole money from the loan shark Noja and disappeared. He funneled the money into shell company accounts and set up a company under a false name to make himself untraceable. He isn’t trapped by illness — he’s hiding from a crime he committed.
His daily routine over those ten years is fairly grim, too. He takes his vitamins in the morning, peeps at the woman next door in the shower, runs on the treadmill, orders delivery. The webtoon has no intention of making you sympathize with this man from the start.
Then one day he sees a man outside his window who looks just like him. Strange things follow. There’s a treatment record at a hospital under his name, from a hospital he’s never visited. A middle school classmate insists he ran into Moonjae recently. Apparently Moonjae attended the class reunion, too. When he finally steps outside for the first time in a decade, he comes face to face with the man living under his name — a man who calls himself the Rat.
Going to the police doesn’t help. The Rat has already had his ID card and resident registration number invalidated, so a basic identity check comes back empty. His parents are dead. He has no siblings. After ten years in hiding, almost no one knows what his face looks like now. The police arrest Moonjae for property damage instead.
The Webtoon’s Moonjae Isn’t a Victim Either
This is where the webtoon turns.
Moonjae once worked as a mentor to amateur writers, and took their manuscripts to publish as his own work. The name “Je Moonjae, successful novelist” was built on other people’s writing from the beginning. His ex-girlfriend, Song In-ju, was one of those victims.
A man who erases other people’s stories and puts his own name on top of them. This is where the webtoon’s reason for calling him a rat starts to surface.
The Webtoon’s “House of Rats” Is a Much Bigger Operation
The further the investigation goes, the further it moves from a single case of identity theft.
There’s an organization called the House of Rats. On the surface, it’s a charity supporting people in difficult circumstances. It operates on a pyramid structure — donate enough or recruit enough members and your rank goes up.
What it actually does is this. It kills people who have committed terrible crimes in the past. Then it launders their identities and hands them out to people who don’t legally exist. Inside the organization, this isn’t understood as crime. It’s understood as social justice.
The drama has Seunggyu’s identity-laundering network, but that’s fundamentally a business. The webtoon layers a distorted ideology of salvation and justice on top of it. That’s why the webtoon’s scale feels so much more social.
The Rat’s Identity — Oh Gi-wan, and the First Je Moonjae
Moonjae and Noja trace a tattoo on the Rat’s wrist reading “Sotae 91” back to Moonjae’s middle school years. One of his classmates in the writing club was Oh Gi-wan.
But Oh Gi-wan wasn’t his real name either.
Moonjae’s parents couldn’t conceive for a long time, so they adopted a boy. They gave him the name they’d been saving for their future son: Je Moonjae. Then a biological son was born — the Moonjae we know.
From that point, everything the first child had disappeared one piece at a time. His parents’ attention. His room. His things. Eventually, his name. Je Moonjae passed to the biological son. And the boy was abandoned at Sotae Amusement Park. The man who picked him up gave him the name Oh Gi-wan — a man who collected orphans, put them out begging, and kept the money.
“Sotae 91” was never a code. It was the place he was abandoned.
The Cruelest Twist — Moonjae’s Trauma Wasn’t His Either
The webtoon’s Moonjae is haunted his whole life by one memory: going to an amusement park with his father as a child and nearly being abandoned there. Chasing a yellow bouncy ball, getting lost. He believes it’s the defining wound of his life.
As he’s dying, Oh Gi-wan asks him a strange question. How can someone inside a memory see his own face?
In Moonjae’s memory, young Moonjae appears as if viewed from outside. That’s because the memory was never his. The boy abandoned that day was Oh Gi-wan, and Moonjae was the one who watched his brother disappear. Once their parents erased the older boy’s existence, Moonjae spent decades turning someone else’s memory into his own.
It fits the webtoon’s core exactly. Moonjae didn’t just steal other people’s writing. He built his life partly out of someone else’s wound.
What the Drama Changed
Who the Rat is. Oh Gi-wan in the webtoon, Seo Yumin in the drama. The webtoon’s Rat is literally coming back for the name he had first. The drama’s Yumin has no connection to the history of the name Je Moonjae at all.
The motive. This is the biggest difference. The webtoon doesn’t build its central motive around a love triangle over Minyoung the way the drama does. Oh Gi-wan’s motive is much more primal: his own life feels unbearable, and other people’s lives look better. That desire sits on top of a past in which even his own name was taken from him. The drama added the triangle around Minyoung and made her death a central part of the conflict.
Sunyong. In the webtoon, he’s Moonjae’s middle school classmate, now a detective. That makes him one of the few people who could compare a fake against the real Moonjae’s face and history — which is exactly why the organization sees him as a threat. He’s lured into a trap, killed, and staged as a suicide. The person who remembers the real Moonjae gets removed. The drama’s Sunyong does the exact opposite, carrying the hope in the ending.
Noja. The drama’s Noja survives and goes home. In the webtoon, he protects Moonjae to the end against Oh Gi-wan’s organization and takes a fatal gunshot. Knowing he’s dying, he hands Moonjae his gun. A man who started out chasing money dies protecting a person instead. In the epilogue, money arrives at Noja’s father’s house with no sender listed.
The final confrontation. A cruise ship to Jeju in the drama; Sotae Amusement Park in the webtoon — the exact place Oh Gi-wan was abandoned.
The Endings Go in Exactly Opposite Directions
After shooting Oh Gi-wan, the webtoon’s Moonjae doesn’t go back to his old life.
He publicly admits to the plagiarism. He returns the money he earned under that name to the writers whose work it actually was. And for the first time, he starts writing something himself, without stealing it from anyone.
In the webtoon, the way Moonjae gets his name back isn’t by legally reclaiming what was taken from him. It’s by acknowledging and returning what he took from others first.
The drama goes the other way. Moonjae eliminates Yumin and reclaims his name, but walks off the ship wearing Yumin’s clothes. He tries to rewrite the second volume Yumin left behind and can’t get down a single line. Then he retreats back into the apartment.
The webtoon’s Moonjae becomes his own person by admitting his guilt. The drama’s Moonjae learns his guilt and becomes the Rat anyway.
Oh Gi-wan’s own end is crueler still. He spent his life under other people’s names and stole other people’s identities in order to reclaim his own — and dies as someone who legally doesn’t exist. He’s processed as an unclaimed body, marked only as “Sotae 91.”
The Webtoon Isn’t a Clean Happy Ending Either
Moonjae starts a new life. The organization is dismantled. It looks like an ending earned after a long price.
But there’s one panel left.
A detective appears, saying he’s taking over the case after Sunyong. He’s another of Moonjae’s middle school classmates, apparently. Moonjae looks at him and feels something is off. The boy I remember didn’t have that face. He turns it over for a moment, then lets the thought go. It’s been a long time. People change.
Right there, the webtoon loops back to its beginning. A man who sees with his own eyes that something is wrong, then trusts the paperwork and the explanations around him over his own memory. Oh Gi-wan is dead, but the structure that produces rats is still standing.
Two Works, Two Different Questions
What the drama asks comes down to who actually lived their own life.
The webtoon asks something a little different. Who owns a person’s name? And what is it that makes society acknowledge that a person exists at all?
Oh Gi-wan was born without a name. He was adopted and became Je Moonjae. That name was taken from him. He lived as Oh Gi-wan. Then that name became a dead man’s too. So he builds an organization that hands out other people’s identities. If society treats a person as nonexistent for lacking a name, he’ll give them one. The problem is that every name has to be stolen from someone. Salvation turns back into violence.
And what Oh Gi-wan did to Moonjae is ultimately what Moonjae did to others, returned at a much larger scale. He erases the name of a man who erased other people’s names. He steals the life of a man who stole other people’s stories.
They started from the same folktale. One became a story about reclaiming your name through confession. The other became a story about reclaiming your name and turning into a rat anyway.
That’s probably why Netflix didn’t simply adapt the webtoon as it was. By making the Rat’s identity unguessable even for readers of the original, the show throws the same question at you from a completely different direction.
Basic Info
Original webtoon: Field Mouse by Ludovico
Serialization: Daum Webtoon (now Kakao Webtoon), February 2017 – April 2020
Netflix adaptation: Kim Hong-sun (director), Lee Jae-gon (writer)
Cast: Ryu Jun-yeol, Sul Kyung-gu, Lee Kyu-hyung
Episodes: 10
Release: August 28, 2026, globally on Netflix
Everything you need to fully understand Netflix’s Mousetrap — what to know going in, the full story, and the clues behind the ending.
Mousetrap: What You Need to Know Before You Watch
Mousetrap: Full Story and Ending Explained
Mousetrap Ending Explained — The Clues You Missed and Who the Real Rat Was
Looking for more Korean thrillers with this much twist density?
Should You Watch The East Palace? A Korean Viewer’s Take
Agent Kim Reactivated: What You Need to Know Before You Watch
A Shop for Killers Season 1: What You Need to Know Before Season 2
Did you read the webtoon before watching? I’d like to know which ending landed harder for you.
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