It is well known that death exists in the world, though no one really ever believes the personified version. Old lore tells of one known as the Grim Reaper; and those that do believe take him to be a malevolent spirit or demon. Neither of which is true, of course.
But the existence of Death is very much real, just not as many would expect or could possibly even imagine. The one who goes by several names: The Grim Reaper, the Fourth Horseman, Death; is, to put simply, the Ruler.
Under him there are several other reapers in existence and their numbers lie in the thousands. They travel around the world, guiding wandering spirits to the other side, and granting them passage in order to prevent them from becoming vengeful spirits. And unlike the lore, they aren't as otherworldly as they appear to be. Some, even manage to live among the living without any suspicion. They can venture back and forth between the World of the Living and the Realm of the Dead.
But despite popular belief reapers aren't just born... they are casted. Reapers are often humans that have made a deal with Death; the deal being an act of selflessness. But the more they live as reapers, the more they forget about their time as a human. But they aren't unsympathetic. Some may come off as cruel or insensitive, but others still try to preserve their humanity. Kass, a relatively new reaper, is an example of this.
Having been a reaper for only twenty years, and despite having no recollection of how she came to be a reaper, Kass still longs to cling on to the little humanity she has left and on occasion finds herself traveling through the World of the Living, hoping to regain the pieces of her mysteriously fleeting memories. Upon doing so, she finds herself an unexpected admirer who unbeknownst to her, has been watching her for several months as she frequents her favorite spot on a lonely bench overlooking a river in a small town that seems much too familiar.