His loss of memory is his punishment for the sins he committed as a King. His proximity to Kim Shin as a roommate creates a "link" of forced proximity that eventually leads to a path of mutual forgiveness.
An amnesiac reaper who becomes the Goblin’s hilarious and bickering roommate.
On the other side was not heaven. It was a library with no walls—just endless shelves stretching into a grey fog. And at the center, chained to a stone lectern, sat a figure so massive that Lonely’s eyes watered trying to see its face. A hand, each finger a fallen redwood, rested on the lectern. From its pinky dangled a frayed silver thread—the other end of Lonely’s link.