It makes sense that Dongeun made Yeonjin her dream. After all, the root of her suffering is Yeonjin. And then Jaejun simply lets her do what she wants. Between the two of them, their influence is enough to not only ruin Dongeun's life, but inadvertently the lives of those they call friends. These friends are all stuck in a cycle where nothing changes, and it is Yeonjin who makes it so. "I do it because nothing will ever happen to me, and nothing will change no matter what." (Yeonjin, ep 1).
The rot in this friend group begins and ends with Yeonjin. Her parents are wealthy, she is pretty, and nothing in her life ever changes. She has never had to work for anything, has never known lack, and similarly, her husband and job were given to her as well. Her power has never been because of who she is, but is thanks to who supports her; first her mother, then her husband. Therefore, she never suffers, whether she is bullying someone at school or at work.
Jaejun has never been challenged in his life, and everything he has has been given to him. he's never really had to work for anything, and that's one of the reasons he hardly values anything, this includes people. He only values his own ego, his dog, Yeonjin, and now Yesol, who he's found is his daughter.
Sara never had to work for anything either, and then comes the point when has to work to set herself apart, to be unique and singular. Not necessarily for herself, but for her parents. Her parents are wealthy, but sara does not seem to have nothing that profits them, except for her art, and that particular talent only manifests when she is under the influence of drugs.
As for Myeongo, he acts as an errand boy. Myeongo's presence reminds Jaejun that he is superior, and leaves him to do his errands and dirty work, just as it was in highschool. Sara and Yeonjin use him as an errand boy as well, and minor criminal activities. I'm sure they are prepared to dispose of him at the slightest evidence that he is linked to something illegal. This is why Dongeun says that he has nothing to lose but his life; he has no wealth nor does he have people who love him.
When they were younger, the violence with which Sara and Myeongo treated Dongeun reflected those who they orbited ie. Yeonjin and Jaejun. The very essence of them has only ever been an echo of a reaction greater than themselves. Sara, though Yeonjin's best friend, is the a representation of her darker side, the cumulation of her evils. I personally headcanon that Sara smokes to forget, to be able to live with herself. Myeongo is the same for Jeon Jaejun, a reflection of his hidden cruelty. I also believe Myeongo drowns himself in alcohol every night until he blacked out because he has to live, not only with the deeds he has committed but also the way he is treated.
The entire group keep Hyejeong around for much the same reason they do Myeongo. Hyejeong is a sort of yes man; she adds nothing to thier friend group, but leeches of them. Lee sara and park yeonjin keep her around because she reminds them they are better than her. Jaejun tolerates her because Yeonjin no longer slept with him after she got married, so he turns to Hyejeong. Hyejeong is aware she is pretty and ususally uses it to get what she wants, a habit started back in highschool to get the keys to the gym from the PE teacher.
A less noticed individual but equally as important is the girl who was bullied after Dongeun, Kim Gyeongran. She still is still under the friends' thumb, though she is hardly acknowledged, and is an errand girl. She works at Jaejun's store, and is seen giving Yeonjin her shoes when she is at the station reading over her news script. I have hopes that she will join hands with Dongeun and drown all of them in a polar night.
All this to say that this group of friends are still trapped in high school, in a never ending time loop. No one realizes it because the only people they accept into their inner circle is each other; its an unhealthy codependency. They may think they have progressed and become successful in life, but notice none of them have lasting relationships except for Yeonjin. None of them have anyone to really rely on outside of each other. Now, Dongeun is turning them paranoid and against each other. When they are isolated and without wealth or the support of their friends? What will they do then?
