I don't know why this drama can have such high ratings, but honestly it has too many issues and very poor writings. And I am just at eps 5.

First, why the ANSP (or I don't remember their names) guys keep looking for the MC around the school for days even though they were asked to stop, do they have so much free times ? lol.
It's actually hard to understand why Lee Kang Moo keeps looking after the MC right from the beginning.
Too many stereotypes characters too.
Worst one is the telephone girl lol, why is she willing to put the girls in danger just because of her stupid ego...
The way she found the bag was kinda stupid too. Why the hell the girls want to keep a bag with cloths full of blood ? Seriously they should have gotten rid of this right away... And yet they decide to hide this bag the day they know the telephone girl found out about them... And somehow by coincidence she was stalking them that night... (was she going to keep stalk them until she finds something ? Its not like she knew for the bag)

As for the day Lee Kang actually decides to look again for MC at school, by coincidence he had to go there for some money... What a coincidence. And then they are still clever enough to raid a school full of girls and put them in danger, while somehow being able to get dozen of people with him ...

As for MC, kinda hard to appreciate him when he and his 2 friends treat them like sh*t, its not like he is still alive thanks to some of them...

We actually have another dumb character, Lee Kang ex fiancee .... Why the hell would she shoot when they go pick the tel ??? I mean even if she managed to kill MC, the other 2 would kill Kang and the girls for sure...

Overall the show abuse too much on the coincidences making them pretty frustrating... And even after 5eps we still don't know what MC wants to do...