This story started off really slow -- each episode they solve 1 person's grudge, and the goal is to solve 10 grudges by the end of the month so the female lead doesn't need to rot in hell.
However, as the grudge-solving goes on we see bits and pieces of the female lead's past... and as we start to put the pieces together, we realize that the story is a lot more put-together than it seems. The foreshadowing that happens in the first few episodes builds up into major plot twists, and the last 1/3 of the show is pure dramatic bliss. If you're into foreshadow-hunting and plot twists then stay on board... it's a really rewarding watch!

Wishing I got to see more of the second couple though :( They're so cute.