The story was so complex, realistic and fascinating at the same time. I've read reviews on different forum to have better comprehension of the story and I'm glad i found this review almost exactly to what I see this drama in general.

THE CASTING & ORIGINAL STORY SET -UP
In a recent interview, PD Ahn said he wanted to work with SYJ. He felt that she was the best actress to play a mid-30s woman at the centerpiece of this realistic drama. “That’s why, from the very beginning, I thought that there was no one else for the leading role of ‘Pretty Noona’ but Son Ye Jin. I only contacted one person [for the role], and it worked out. She decided to take the role even after seeing all the negative sides to it.” He added with a laugh, “I was really surprised.”

SYJ said she also wanted to work with the director. Her fellow actresses gave him high marks. And when she was recruited for the series, PD Ahn promised he would do things so she could meet her goals. As a result, the series was shot more like an independent art film. There were little wasted scenes. And the mood on the set was fun but professional.

SYJ is a professional. Her reputation is to immerse herself in her characters. She was aware of the negatives of JA (her life, her decisions, her mistakes, etc.) He claims the scripts were all read in full in October, 2017 (but does not say if the scripts were changed in the end).

In initial filming before the premiere, JA’s character was described as a hard working person with a lonely personal life where she stares at empty bottles of liquor. She is a typical South Korean woman in her 30s who feels emptiness in her heart because she doesn't feel accomplished in either career or love which every woman around her age can empathize with. Son Ye Jin is showing so much motivation and effort as she is always holding onto her script and having numerous discussions with the director on expressing her character more fully. She is doing a great job in portraying Jin-ah's change of emotion with her detailed acting and really becoming the character. Everyone should be expecting great things to come out of this drama,” a staff member said.
At the beginning, JA’s situation can be summed up as follows:

1. She is 35 still living at home with her parents.
2. She is going out with a terrible BF who has cheated on her after she slept with him (meaning she was serious about the relationship but he was not).
3. Her mother is pushing her to marry the terrible BF because of his status and JA’s age.
4. She is stuck in a dead end job subject to work place harassment and takes blame for others’ mistakes.

JA character is a meek, introverted, weak, hard working but repressed follower of society norms. She really does not talk about goals or a future. It appears she has resigned herself to an unhappy life because she is trapped in a culturally oppressive and socially conservative paternalistic world.

The show was always set up to be JA’s journey to self-awareness and independence. It was meant to be a realistic sad story.

What hooked viewers in the initial episodes was the chemistry between JA and JH. It was an unintended consequence because it masked the original story line and theme. PD Ahn stated in that recent interview that the theme of the show was the simple question:

“Are we really in love?”

THE INITIAL CHEMISTRY

If you look objectively at the beginning of JA and JH’s romantic relationship, it was a quick and burning passion. The reason for JA was simple: she was coming off a dead cat bounce relationship with her cheating ex-BF. Since her mid 20s, JA had been groomed by her mother to go out with a certain kind of man (one of status, means and upward mobility). JA’s only hope with these blind dates was that the man would “like” her. JA went out on those dates not out of a search for love but obligation to her mother. JA must have seemed that this current ex-BF was her best shot since she was serious enough to slept with him but his betrayal left her bitter, angry and alone.

JH returns to Korea after 3 years in USA. He is friends with JA’s brother, SH. He knows JH dates many women (because of his looks and charm). He knows he has a stubborn temper. JH is young and carefree in YOLO life style. JH grew up without parents so it appears that he is still harboring abandonment issues. He had dated many women in the past, but apparently could not get beyond 3 months (which is interesting since the 100 day mark in Korea is a milestone of a “serious” relationship.) He is charming, attentive, but also selfish, temperamental and paternalistic.

In a chance timing of motive and opportunity, JH returned to Korea after three years, and the first cute woman he saw he went after (surprising himself that it was his noona.) The surprise flirtation and familiarity was the spark to set them on a quick path to become lovers.

JA and JH get caught up in the mystery, excitement and secrecy of their romance. So did the audience. It was clear that JA and JH loved being together. It was an infatuation.

Attraction? Yes, they both complimented each other about their appearance.
Escapism? Yes, they both were coming back from negative experiences to find comfort in each others’ arms, away from their daily grind and problems.
Infatuation? Yes, the hot and secret aspect of their intense and short lived passion for each other.
True love? No. Even though viewers were caught up with the initial passion, the couple’s relationship was foreshadowed to be doomed. As reality encroached on their secret life, real serious issues arose between their family members and friends which the couple did not or could not discuss and work out together.

How each character viewed their relationship was telling:

JA did like the fact that a younger man found her attractive and desirable. It may have been a long time since a man approached her (instead of through blind dates). She wanted to keep it a secret because she knew it was all merely fun: companionship with benefits, not a serious relationship. Also, JA wanted to keep it secret because she knew the negative ramifications to her family and friendship with KS.

However, JH did not want to keep it secret. This showed his naivety. His character always lived in the moment, not thinking long term consequences of his actions.
Their relationship turned into a cliche teenage crush. And as the episodes went on, there was no intellectual, emotional or spiritual growth in their relationship. They never discussed a shared future together.

THE MIDDLE CONFLICTS

The greatest problem with the story was JA’s interaction with the people around her. It was an intentional portrayal. She was an apologetic follower. She rarely stood up for herself. Her decision making was mired in self-conflict, self-doubt. She thought the world viewed her as a commodity and not as a person or a woman.

And this was embedded in how she dealt with her personal life, including her affair with JH. The series lacked deep discussions between the characters that is the foundation for serious relationships.

JA was conditioned to be subservient and accept what others told her.

What were the major issues in JA’s life?

1. Her mother’s desire that she marry the “right” man. But after a serious of loser boyfriends, JA had basically given up on a chance to meet Mr. Right, someone she could passionately love while be acceptable to her family.

2. Her job was becoming more unbearable. The demands and blame she took for other workers mistakes were mounting. The harassment of her by superiors was intolerable. She was in a dead end job with no real chance of promotion.

3. She had few friends. KS was her best friend who she could confide in. It seemed that JA had a hard time making new friends. When she does make a close friend, she tries hard not to break that bond, even it means hurting herself in the process.

4. She has a maniac ex-BF who wants to get back together or ruin her life.

How did the couple “work” to resolve these issues? They did not. JA and JH were merely apologetic to JA’s mother about their relationship, but did nothing to convince their families that they had a future together. JH did nothing to help JA resolve her work place issues, or support her if she wanted to change career path. JH brought JA to meet some of his friends (on the overnight trip) but JA did not do the same. (this shows JH was more into the relationship than JA). JH got jealous and violent about JA’s ex-BF which contributed to conflict between them because he did not discuss beforehand with JA his actions.

The breaking point was JH demanding that JA come to him to the US. Of course, JA said no. She felt insulted that JH’s solution was to run away from problems. (Not to mention that it would be impossible for JA to suddenly move to the US with no job, no spouse, and no money with the country’s current immigration policies). JH solution was that JA would be there for him. He was angry that she rejected his solution. He never understood her position, her feelings or her long term goals.

The couple’s initial passion glossed over several important aspects missing from consideration on whether this was heading toward a serious relationship or “true love.”

1. Communication. Their communication was superficial. They did not discuss important issues or ideas which represents mutual immaturity. They never opened up to each other on what their personal goals were (job, career, changes, etc.) or how they wanted to achieve them. They never really understood the other person's emotional state, and they never deeply discussed how the other person felt in a given situation. I recently read a psychological study that concluded that many people told “white lies” early in their relationships as a means of making themselves more “attractive” to their partner. Usually, those minor lies were used to build up a person’s self-esteem or enhance their traits (prospects) to the other person. But in JA and JH case, those lies were meant to hide the truth and real feelings (under the fabrication that they did not want to “hurt” the other person.) Instead of talking things through, they glossed matters over and then began to mistrust each other. The each called the other “childish.” They could not talk to each other about serious matters because they were caught up in the teenage aspects of a romance fairy tale.

2. Compatibility. Sympathy, friendship and like-mindedness are critical foundation blocks to any serious relationship. JH knew about JA’s situation at home and at work, but his support for her situation was tempered and distant. He wanted to control the situation. Likewise, JA did not seek out his advice on how to find a solution to any of her problems. Also, JH did not ask JA for advice on his work, his options or his troubles. JA and JH knew each other before dating, but there is no evidence that they were “friends.” Friends have mutual interests, concerns, ambitions, support, trust, varied experiences to share. JA and KS had serious discussions as friends. JH and SH had serious talks as friends. But JA and JH never had such a connection because such “real life” discussions would have interfered with them hanging out together and having fun as a new, care free couple.

3. Commitment. JA and JH never discussed the big things like their expectations, marriage and family life together. JH’s solution was unilaterally demanding JA move with him to the US. He never asked her hand in marriage. Some women would call this behavior selfish, inappropriate or “clingy.” JA’s solution to move out of her house so she could continue to date JH but not live with him showed that she was not ready to fully commit to him (she would later say she had things she wanted to be independent to become strong.) They never had the heart-to-heart discussion of “making plans” together as a couple. Even though both are adults, they both had serious maturity issues.. (Continuation at the comment section)