The Secret of Reincarnation

In my world, ghosts are not scary things. They are just "people" in another world who can live in peace. Ghosts come to the human world through reincarnation, and people go to the underworld through death. It seems like a simple reincarnation, but there seems to be an unknown secret behind it. What kind of ulterior truth is hidden under the hypocritical mask of reincarnation? Is the purpose of reincarnation a helpless act or has another hidden agenda? The protagonist of the novel takes you to explore the truth about reincarnation.