This was great entertainment but I think they tried too many stories and they loose a bit of intensity and you also forget at times about events that get no closure.
I loved the main story line if the professor, the academy, the mums and of course his love story. It was quite refreshing watch a more mature couple although they still insisted of making them both completely inexperienced and new to love even pushing their 40s. That's an obsession of koreans and their idea of virginity, but as unrealistic as it can be.
Other than that it was great, despite the 10 years gap between the ages of the leads it looked somewhat believable, but not for their chemistry but for the absolutely amazing acting, they are very experienced actors and you can tell.
The secondary storyline with the teenagers ( love story and school bullying) is another one, and that was very interesting as well ( it was worthy of it's own drama) but the execution wasn't perfect due to the series focusing on all the other storylines so it was left incomplete and the finish was rushed.
The big surprise was the serial killer twist, which was extremely rushed and packed in the latest episodes which made it completely unbelievable and wasn't carried on smoothly throughout the show. I don't think they did a good job with this part but this is what we got.
Overall original and funny but I was expecting more.