Sooyi

Lol I was having an idea that the drama will end with a cliffhanger with Hongju pregnant with Yohan's child, and it sorta happened right now? However, now that Bareum has changed, it leaves room for more development to the plot.

Hanguk was supposed to represent envy and the story was "The Goat and the Donkey". It's about a goat who was jealous of the donkey kept by his owner because he ate better food so she tricked the donkey to get severely injured, yet her plan backfired when the healer who was treating the donkey said that he needs a cure made of her lungs to recover from his injuries. So Hanguk is the Goat (as shown by his mask) and his half-brother is the Donkey. The Cross Killer managed to track down his biological father's family and kidnapped his half-brother. The boy in the abductor's fake video was him. The Cross Killer taunted Hanguk to be envious of his half-brother so that he can be spared but Hanguk refused to be so and said that he pities the Cross Killer.

The tale for Moowon, Moochi's brother is "The Wolf and the Seven Young Goats". His stomach contained stones and it mirrors to the vengeful act of the Mother Goat who filled the Wolf's stomach with stones in anger(=wrath) after freeing her children, and subsequently threw the Wolf into the lake, killing him.

It's pretty obvious that Yohan is the Cross Killer and thus Jaehoon because his mother had a flashback of her strangling him after he tried to bury his brother alive. He was stalking Bareum all this time and he came to his home when he and the team wasn't there. He was also at the prison the day Chiguk got murdered and nobody suspected him because he went inside unrecorded as he went through the employee's entrance (he "forgot" his ID so his friend, the prison doctor, suggested he come with him through the employees' entrance as they don't check IDs there).

Moochi finds out that Yohan was the person who last met Bongyi's granny due to tracing the yogurts in her bag to the house cleaning agency (he remembers the yogurts that went missing from his last visit to the agency). He breaks into Yohan's house and finds bloody shoes in order to pin him as the suspect behind the Cross Killings and Hanguk's abductor.
Hongju seems to be pregnant(?!) with Yohan's child because the pregnancy test showed two lines.

Yohan went to Bareum's house to confront him for once and all, but Bongyi happened to be in the house because Bareum suggested she live with him because she can't manage with her injuries. She was trying to leave and Bareum managed to return home in time and helped her escape. Bareum decided to remain and stop Yohan. Bongyi did call Moochi beforehand so he came to Bareum's house and he saw Yohan bludgeoning Bareum (on the head as the camera pans down). He shoots at the doctor and the second shot hits him at the waist. The two men rush to the hospital. Bareum is revealed to have survived (obviously) and the bird Beongyi is in his hospital room. It's chirping and Bareum approaches it and brings him to him and.... breaks its neck before tossing it out of the window. We hear Bareum saying "Gosh, it was so noisy".

Spoilers for episode 6

Maybe it was simply a mistake due to desperation but I found it odd that Bareum didn't notice that the child (the boy who impersonated Hanguk in Moochi's video) put the parcel in locker 14 while the killer/Hanguk's abductor put his in locker 13 that the delivery man retrieved.

I think it was Shin Sang too due to his knowledge and if you listen to his voice, though modified, you can make out his tone. The anonymous informant has a witty tone like the detective.

I think the boxer represents revenge. All the victims, except for Bongyi's granny, are people who have not succumbed to their sins. Remember the boxer's sister was killed by the Headhunter, but the boxer didn't try to get back at him even though he was arrested and sentenced to be executed at the time.
In my opinion, Hankook was a bait to show the killer's grand picture for the murders to the public and to break down Moochi.

I think they're supposed to represent Lieutenant Park's wife and his daughter, and they probably got kidnapped in response to him provoking the Headhunter on TV. I guess he managed to only find his wife, and from what I remember, his daughter is considered dead because following the arrest of Han Seojun, the Headhunter, the police uncovered human remains at a mountain and the DNA had a match with Lieutenant Park.

There is also vanity.

I feel like envy is Moochi's co-worker/former friend who is always angry at him for butting in his cases.

The whole episode felt like one long monologue in a play, and Lee Heejoon managed to pull it off. It seemed like it was excruciating to film it.

Episode 5 felt like the ending of the movie "Seven" except that it was Moochi's brother who had to feel wrath, not Moochi himself.
I suspected early on that the murders were based on the Seven Deadly Sins due to the theme of religion but I couldn't see the references. I think it's a rather overused trope but it was masterfully explored in "Mouse".

Basically, the killer abducted the boy to showcase his power as the Watcher, Judge and Punisher and that he is above the people.

Something I don't understand is that I thought the Boxer (the brother of the woman who was killed in the snow) represented wrath (due to being burned alive and the fact that fire is often associated with rage) but after reflecting on the matter, I think he represents "revenge". He didn't try to avenge his sister's death and the Bible which was found at the murder scene marked at the passage "An eye for an eye / A tooth for a tooth" was found. It was also probably a scheme for the killer to test Moochi's abilities and subsequently lead him to the six murders.

Now the question is how did the killer/abductor found out Bareum's idea of impersonating him in order to lure him out? Who is the next victim?

I feel like the goal of "Mouse" is not just to find out about who is the killer but also to understand his mind and how to outsmart him.

I wrote spoilers down below if you're interested.

Yes and it's vanity. So I guess the succeeding mission is to find who fits the profile of vanity.

-The Single Mother: "The Red Riding Hood" -> lust
>>>When the woman was still alive, she worked in the kitchen of a hostess bar (it's a bar where men can drink in the company of women, and it has become a joint for prostitution). A client was interested in her but she refused his advances because she didn't want to disappoint her daughter. The wolf in "The Red Riding Hood" represents lust and the woman was found wearing a red hat.

-The Homeless Man: the Korean folktale, "Silver Axe and Golden Axe" -> greed
>>>The homeless man was in fact a business man who made frequent donations to an orphanage. I think his company suffered bankruptcy and he had to live in the streets (but he still gave all of his remaining money to the orphanage). Even then, he still helped other people in the same circumstances as him. From what I remember, "Silver Axe and Golden Axe" is a Korean folktale about a young woodcutter who met a mountain spirit one day after his labor and the latter man insisted on gifting a golden axe and then a silver axe successively. During both times, the woodcutter refused as he was satisfied with his simple old axe, and the mountain spirit, touched by his sincerity, decided to give both the golden and the silver axes.

-The Mukbang Streamer (young woman who went out jogging): "The Fox and the Grapes" -> gluttony
>>>The young woman did mukbang livestreams so she could earn money but she spat everything out after eating because she didn't want to gain weight. She represents the fox's hunger for the grapes in "The Fox and the Grapes" (the fable is hinted through the location where the woman was found, the vineyard). Interestingly, before her, the killer previously approached another woman who is an aspiring model (so she appeared in magazines) and used to work at a supermarket, and he therefore ordered her to eat all the food at her disposal. She painfully obeyed his command so she was spared.

-Ba-reum's friend: "The Emperor's New Clothes" -> pride
>>>Back in high school, Ba-reum's friend, Chiguk, defended Sung Yohan (it's confirmed it's him) from his bullies who wanted to "do a noble deed" by killing him, the son of the Headhunter. However Ba-reum's friend did not bask in his glory as we can see how he said it was Ba-reum who stopped the bullies. Chiguk is unlike the Emperor in "The Emperor's New Clothes" who wanted to bask in the attention he received from his extravagant clothing. This is why Chiguk was found without his uniform.

-The Factory Worker: "The Ant and the Grasshopper" -> sloth
>>>The Factory Worker was insistent on making his ends meet through proper hard labor just like the ant in the fable "The Ant and the Grasshopper". He wanted to prove that he can be successful though he was born poor. A grasshopper was put in his mouth to refer to the tale in question.

So basically our killer in question considers himself a representative of God on Earth and a judge. He "punishes" the people who have not succumbed to their sins which are the Seven Deadly Sins. And the clues pointed out to items which referred to items which appeared in various fairy tales which have a morale.
-The Single Mother: "The Red Riding Hood" -> lust
-The Homeless Man: the Korean folktale, "Silver Axe and Golden Axe" -> greed
-The Mukbang Streamer (young woman who went out jogging): "The Fox and the Grapes" -> gluttony
-Ba-reum's friend: "The Emperor's New Clothes" -> pride
-The Factory Worker: "The Ant and the Grasshopper" -> sloth

The killer knew his victims because they were introduced through different forms of media such as television interviews, radio, blog entries, livestreaming and newspaper articles. This is how he picked them.

Moochi thought that the boy the killer abducted represents wrath because his father abandoned him just like the father in "Hansel and Gretel" and he was lured away from his mother through bread, so Moochi theorized the killer wanted the boy to feel anger toward his father for giving up on him. But wrath was actually Moochi's brother who has forgiven the Headhunter and has led a dutiful life in spite of losing his parents and being crippled. Moochi's brother is being held hostage by the killer and the whole encounter is on live, and the killer demands him to get angry. Moochi is of course horrified and pleads to his brother to vent out his rage, but Moochi's brother is adamant about letting go of his grudges till the end and he gets killed.

Spoilers for episode 5

You don't have to be sorry because I like reading people's opinions of the drama :)

I came up with my initial theory because from the way her family acts around her in episodes 7 and 8, Grandma cannot recognize them due to her Alzheimer's. But if she was able to recognize adult Hayoung and great-grandson Seongwoo, it means that she got diagnosed rather recently. So it's strange how she is still unable to register adult Hani from what's suggested in the teaser.

To be honest, I'm not sold for the idea of teen Hani changing the timeline because it'll nullify all the efforts adult Hani has put into rebuilding herself, and therefore the show's message of self-love and hope to start afresh will have no meaning. So this leads to my other theory that maybe teen Hani is from an alternate universe and there, she can prevent her father's accident? Like you, I hope the writer doesn't mess up the gimmicks of time-traveling and the butterfly effect.

I don't understand why they're called "episodes" either because when you watch one "episode", there's a message which says "part 2 will air shortly" in Korean. It's confusing XD

I'm very intrigued about the whole time slip in the drama. From what I see, teen Hani's cellphone is the device that enables her to time-travel as her phone's battery is shown to have died and her grandma was furtively searching for its charger. According to the teaser of episode 9, Grandma wants to give it to teen Hani and cannot seem to recognize adult Hani as her granddaughter while she could discern all of her family members fine, including Seong-woo. So all of these findings led me to think that adult Hani is probably a "glitch" in some way (something that wasn't supposed to happen) and teen Hani could prevent her father's death because Grandma kept on saying that she'll "fix" everything and was pitying her (I'm guessing she was probably alluding to Hani's guilt and loss of drive in life following her dad's passing).