KDrama Big Mouth Review: Why So Many Plot Holes?

Big Mouth or 빅마우스 (Bigmauseu) in Korean is a south Korean thriller, a hardboiled crime drama starring Lee Jongsuk, Im Yoona, Kim Joohun & Yang kungwan. It’s directed by Oh Chunghwan & Bae Hyun-jin. Considering Oh Chunghwan has worked with Lee Jongsuk in “While you were sleeping” and his previous drama “Startup” did very well, this drama starring Jongsuk again, especially as a comeback after Jongsuk’s military enlistment, came with a lot of expectations. Before we jump into the Big Mouth plot holes, let’s take a look at the good things about this K-Drama.

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Big Mouth

It’s a clever title for the series where Big Mouth & Big Mouse are both written the same way in Korean; the plot also started off, including this wordplay pretty well. The mystery and storytelling in the first few episodes keep throwing Park Changho (Lee Jongsuk) into one mess after another in prison, as if being wrongly accused wasn’t good enough. As viewers, we are happy to see the female lead fall into action in almost equal importance as her counterpart, a married couple in a sensible relationship and understanding. Ko Miho (Im Yoona) is a strong character that starts to solve the mystery of the web that her husband has been caught in. 

Changho and Miho work from two different angles to unearth the missing pieces of his false incarceration. Choi Doha (Kim Joohun) & Gong Jihoon (Yang kungwan) add twists and keep up with the mind games thrown at them. The show starts to shape up really well and is quite exciting. Gong Jihoon’s character was so entertaining that I waited for his screen time as his uninhibited reaction to any situation was unpredictable, even though he was almost always morally compromised. Then the big puzzle, with every episode either adding a name or clearing a name to the show’s big question, “Who is Big Mouse?”

Korean Drama

At this point, everything is going well for the tv series, and we, the audience, are turning into Big Mouth just like Park Changho. Maybe around 4 or 5 episodes in, I was really that Big Mouth, telling others to get watching this drama, excited for how the show was shaping up. With an experienced acting cast and good production, this was promising. Rating of the show was going up – Jungsuk’s comeback with a strong series and Yoona already having a fantastic year, with a Girls Generation comeback, Confidentiality Assignment 2 and now Big Mouth. The show kept this momentum for another 5 episodes till perhaps episode 10. Then starting from episode 11, the downhill journey began. 

Now I really wish I could ask the writer Kim Haram, what in the world happened from that episode onwards? The drama till then had hinted at so many clues, mysteries and twists with a sense of assurance that it had answers to them. As honestly, they were not really some mind-bending questions. But it turns out that in the last 6 episodes, we are not only left in the dark for most of the open threads but also treated to some convenient & lazily added twists. It left me wondering if the writer changed or if it has started to morph into a different show. What began as a promising tight storytelling turned into a downward spiral with loose ends dangling. Here are some Big Mouth plot holes and unanswered questions that the show decided to bring up but never resolved or gave any clear explanation.

Big Mouth: Plot Holes Explained

Why did Big Mouse Noh Park’s daughter die? 

Yes, we get a two-second scene of her murder suggesting it was done by Chairman Kang’s son, attributed as one of the victims of his serial killing. But if the whole show was a consequence of that revenge, then the audience deserves more than a two-second shot and some backstory around it.

Big Mouth: Who is Chairman Kang’s son?

A character that was not even cast was showered with a lot of mentions, especially in the closing episodes. Even hinting at inmate Tak Kwangyeon taking the fall for him as the psychopath serial killer.

Why even mention the possibility of dragging Choi Doha over an inheritance lawsuit as a highlight? 

Chairman Kang’s estranged serial killer son filing a lawsuit against Choi Doha over the inheritance issue in the last episode delighted Gong Jihoon. Why give it that much screen time and writing when it was never used, or he was never meant to be revealed before the end?

No one seems to be bothered about Hyejin.

The missing Hyejin thread or her murder is never touched upon again after putting us through psychotic and brutal domestic violence scenes.

Big Mouth: What is the content of Seo Jaeyoung’s papers? 

This made an appearance in one dialogue in the finale. That it was the smoking gun that helped relate NF9 to the cancer patients in his hospital. But honestly, we knew that from the beginning, didn’t we? This paper was always meant to have evidence linking NR to the cancer patients. What did it really have that stunned Hyun Juhee when she looked at it and led to the destruction of the secret lab? The paper and Seo Jaeyoung’s death got Changho into all the mess in the first place. 

Choi Doha’s quick death.

How long has Choi Doha unknowingly been poisoning himself with the toxic pool water? As he seems to go into a pretty quick death! 

How did Changho even find the location where Choi Doha had hidden the gold and the papers?

The show is in a hurry to wrap up everything in the last 3 minutes after Choi Doha’s death. Everything just falls into place. No explanations. We are running out of time.

What in heaven’s name was going on in the secret lab? 

When convenient, the plot makes such things essential, and when inconvenient, and details are expected, the plot just erases its existence. Bravo!

Can a person with a false identity be the Mayor of a city?

His false identity was hyped up quite a bit until it amounted to no consequence. Isn’t that a great weapon to bring him down? Not enough evidence, you say. 

Big Mouth: What happened to the real Choi Doha’s grandfather?

The real Choi Doha’s grandfather was taken to a safe location to reveal the Mayor’s true identity? The show never used that, but it spent a ton of time on that thread. What happened to him?

How is everyone from Chairman Yang’s gang out of prison?  

Understandably, Yang Chunsik was released as his prison sentence ended, but how did all his minions/gang members get out simultaneously?

No repercussions after a prison riot.

There are no consequences faced by the inmates or the prison guards for riot and treason after episodes 11 & 12. Which includes the death of an acting Warden of the prison. Instead, many inmates are free, out and about with Changho henceforth! (Remember the consequences of a riot in Orange is the New black? Things that tv dramas teach us!)

Park Yoongab, a free man now?

Wasn’t Park Yoongab out on bail? So he is also a free man now? Maybe it wasn’t as crucial to Changho’s arc, but such mistakes are plenty in the show.

With so many unresolved issues and bringing in character mentions of a serial killer halfway into the finale, I almost thought we would go into a season 2. But the ‘Deus ex Machina style pool water radiation poisoning that worked incredibly quickly and killed Choi Doha seemed to put a full stop to any further storytelling.

Big Mouth plot holes explained

There is no end to convenient narration just to fit the current plot needs. The most significant example being Ko Miho’s onset of Stage 4 cancer. A metastasised cancer stage doesn’t happen overnight for her to reach a bleeding nose and gums. As soon as the inmate Tak Kwangyeon asks her about the symptoms, she notices the same, maybe that very night. Also, her progress to her death is shown unrealistically. Changho’s acceptance of his wife’s illness and even the scene beside her deathbed is quite rushed. 

Lee Jongsuk’s vulnerable, crying scenes are gems in his previous shows. But let’s not even go there; the vulnerability Chongho shows with Miho is something that got us every time in the earlier episodes. But in this finale episode, a scene where he is losing her for good is quite underwhelming. Honestly, director nim, what happened? 

Although Miho remains a strong female character till the end, she did not have to be sacrificed in the usual female trope narrative for the male lead to reach his expected peak. It was definitely heartbreaking to see an excellent K-Drama couple getting a disappointing ending; right couple, wrong drama!


The show will sadly go down in the list of ‘best starts’ with ‘worst ends’. The show had high ambitions to prove certain aspects of society. It wanted to show the evils of power & money, corruption, a flexible legal system, the upper social class’s disregard for the life and wellbeing of others, and Suffering caused by the inorganic socio-economic growth of a city with no accountability. Changho finally accepting his role to fix and help with some of these issues by being the good Big Mouse that Miho hopes he would be. All is well with intentions and even tight storytelling initially, but it got lost along the way with very lazy, mediocre and sometimes illogical execution to get to the point. 

Yet, I still enjoyed the first 10 episodes, the thrill of second-guessing who Big Mouse was. The excellent acting cast that brought the characters to life, characters that will always be memorable. I enjoyed seeing Lee Jongsuk and Im Yoona as a sensible yet fun pairing. Yoona’s acting has risen up many notches in this series. And of course, I was delighted that my favourite character got everything he wanted in the end – Gong Jihoon for the win! 

But jokes aside, Big Mouth, a show that had the potential to be 2022’s most recommended and talked about drama, will now be left in the list of – ‘Mediocre Shows Of 2022’ thanks to its slippery slope at the writing desk.

What were your thoughts on the plot and ending of the K-Drama Big Mouth? Have anything to add? Do drop your comments below.