I think this drama suffers from a number of flaws, just from my personal point of view, and I do not understand why it has such high ratings.

First of all, if you're not a fan of noona romances, you would not like this. I do not have problems with age gaps IRL, but I just don't like huge age gaps in my dramas. In this particular case, the actress, while being a fine woman and good at her craft, I'm sure, just somehow felt miscast for the role. She looks and feels way too old for a romance drama of this type. Sometimes it almost feels like she could be the male lead's mom or aunt. The pairing just felt cringey for me. And this is not a prejudice against older women falling in love. There are other dramas where this is given much better treatment and the romance is more age-appropriate, or the actors are better cast.

My second issue is I just did not like the male lead character at all. Not the actor per se. Just the character. I didn't hate him. But there was nothing about the character that I found attractive. He's an okay guy, a fine teacher, but other than that, the character was not developed fully and felt flat and one-dimensional almost. Even his supposed main selling point, his mathematical brilliance, was somehow not utilized enough to make you swoon for him. So with the ML's character not fleshed out and the FL being miscast, the main romance just did not do anything for me at all. Many instances where the FL, who is very ahjumma-like, is acting like a schoolgirl just felt...cringey.

The character of the younger male lead is also poorly written. In a way, he's worse than the main lead because the way he's written, he is not just undeveloped and quite generic, but he also has some glaring character flaws. After the exam fiasco, he resorted to avoidance instead of facing the issue head-on. In the interest of inserting some social commentary about how Korean students suffer from pressure exerted by parents, the writers turned him into a cowardly and immature boy who could not even be open and honest with his supposed best friend who he knew was also suffering and confused due to the circumstances. Just not someone I'd imagine falling in love with. The second teenage male lead had more spunk, more sense, and was at least always there for the female lead. Anyway, both male leads were too bland and uninteresting, and not well-developed, IMO. Just poorly written characters.

I also had some problems with the portrayal of the FL's brother. Was he supposed to have Asperger's? High-functioning autism? Somehow I feel like the portrayal was inaccurate, but I am no expert in this. And I also feel like the actor was miscast. I mean, I'm sorry. He's a fine actor. I've seen him in other dramas. But it would have been better if someone...more attractive were cast in the role so that we could swallow the sudden romance later on. That romance with the FL's best friend just felt too sudden, too forced, and just totally unnecessary. The fact that he said he treated her like an older sister all his life didn't help.

The plot itself is nothing special. It follows the usual format of the new spate of romance kdramas, where the main leads get together at episode 10, after which the plot devolves sharply into a not-that-interesting murder mystery, which, in the case of this drama, was resolved in a totally unsatisfactory way. I guess the main point of the drama is to critique Korea's obsession with academic excellence and tutoring services, and I guess they were able to get that across, at least, but the rest of the drama just feels uninspired and not that interesting.