Thousand Years Promise: Book One: Book of the Guardian

About a strange man who runs a curiosity shop and is trying to help troubled people from supernatural phenomenons. As the story goes on, his intertwined past with a group of protectors (known as the seven pillars of the world) who have been shielding the world from negative energy since ancient times, unravels. And his tragic past with one of the protectors came back to haunt him after a thousand years along with a promise he tried to keep at the cost of his life.