Let's be honest, this show is not going to win any drama awards and there are some story telling issues but I gave this show a high score because it is true to its own narrative. I consider that a nice touch as a lot of c/t-drama starts off with one narrative and ends up with a different genre unless they pull it all back in the dying moment of the show. That can be disconcerting, to say the least.
Being a youth focused show, the plot is centred around life at school and university with a "... 3 years later" time skip in the end to tie things up and give everyone closure. The OTP were cute together and have good chemistry. The FL can be a bit annoying as she talks too fast and too much and was tomboyish but that's her character. The most important thing is that both of them are flawed (unlike some other youth drama where one half is amazing and the other is hopeless). In their case, the sum of the whole is literally far greater than their individual merits, they knew it and talked about it regularly.
As I mentioned before, the writers held firm to that narrative. There were minor misunderstandings or challenges to their pairing but they exist only for each other and their faith and trust in each other was unshakable (well, 90% of the time ;)). From that bond came a great deal of growth, both personal as well as in their careers. Even when the ML (handsome and smart) grew out of his shell, he only had eyes for the FL. He never waver for one moment. The FL is also totally into the ML but her character flaws make her tough on the outside but fragile on the inside so there were some initial doubts. However, his presence anchored her being and smoothed her rough edges. In turn, her love and support allow him to overcome his social phobia and lead a successful life. Both achieved a great deal more than if they'd never met.
As you would expect in such a drama, there was little angst. They resolved their issues quickly and what enemies they had, did limited damage and most saw the evil of their ways and made amends. Some even became fast friends! Teachers were all positive influences and only want to see them succeed. Lots of feels in those formative years.
What was a bit annoying was the 2OTP. Their failed attempts at having a romantic relationship was painful to watch, especially when it dragged on for 25 episodes. Why was the 2ML so thick and blinded to the feelings of the 2FL is beyond me. When he did "discover" his feelings, it just seemed to be a bit too convenient. It was like nothing was there one minute and then after seeing the 2FL with another dude (whom he more or less pushed into 2FL's lap), he just said he thinks he likes her after all, did a 180 degrees and chased her aggressively. Really? What miracle water did he drink (PPL in-joke)? Anyway, that paved the way for some cute 2OTP moments for the last few episodes. Even with all the pairings, there is limited skinship. A few kisses towards the end of the show but there were lots more failed attempts and pull backs.
One last observation, in this type of drama, the elderly actors tends to be the screen stealers (either for good or evil) but in this case, the FL's younger (half) brother (~10 years old?) was a gem. He was wise beyond his age and his acting was sooo good and on point.
In the end, it was happy endings all round. Every loose ends tied up with pink bows. It was a drama that you won't recall many highs or lows but will remember with a feeling of fondness and a bit of wistfulness. Life is not meant to be easy but for a little while, the world was a better place where two imperfect characters became a perfect whole.