The story line is based Buddhist teaching where after death humans will need to face 7 trials of judgement to determine whether you should be punished or released.
As you know, Korean movies usually are quite sentimental. The last few trials are related to the family. Hence, it's quite saddening and touching. Most of the people do cried along.
The trials are designed to judge whether or not you are guilty of any betrayal, indolence, violence, deceit and so on. So, while watching, you will also be thinking what have you done so far and have you left any regrets? It's kinda creepy when you started to think or maybe it's time for repentance.
For me, this movie is okok only. Not that very very very nice type. But it's worth watching so you could reflect it on your own.
reference: https://www.hollywoodreporter.com/review/along-gods-two-worlds-film-review-1071209