This drama is peculiar. Very.
I had trouble understanding what the nurse Ahn sees are ghosts, or phantoms, or a different life form. In the beginning, I was tricked into thinking maybe it's just all an imagination of nurse Ahn. That she is suffering from 8 th grade syndrome. But it's not.

As I said the story is peculiar. But still fascinating! It is novel; something you won't see quite often.
The whole story revolves around the school, which was built over an infamously mysterious pound. There are jellies, there are people who can see them. Some people who protect other people from the malevolent jellies and some who use those jellies for their own selfish purposes. The main male lead has an unusual power which can recharge the powers of those who can see jellies.

After completing the drama, there were a lot of things left unanswered. There is still a list of mystery surrounding the school, the people who are trying to control the school's power. The male leads power. Etc.

So go ahead and watch the drama. It is a fun watch, of course. The acting is nicely performed. Unusual story, eerie setting, uncanny magic, and peculiar characters will surely make it a worth watch.
It is only 6 episodes. Plus there might be a second season coming.

Jelly out.