So, it looks like Death itself has her "help" out by guiding individuals to meet their untimely end. Any association with said girl will eventually lead to your end.
I honestly don't see this as horror or scary at all. More, I feel a strong pang of sadness for both. A man overworked wanting to basically do a bucketlist of things he wants to do. A girl effectively with no family (save her little sister) whose only real peace is being dead.
Both need each other. Where it will go and how it will end for both, I can only hope for the best.