Underworld Courier

In this world, there are many unknown professions, and there are also many unknown and strange things happening. If one day you see someone smile at you and give you an envelope without the recipient and sender written on it, you must not accept it. Because then, it is likely to be your death. If one day, when you come to an alley that you cannot walk out of, don't walk around randomly, because then, maybe the ghost is playing a little joke on you that you can't understand... Life is so fleeting and there is no need to marvel at the many strange things in this world. But when this kind of thing really happens to you, who can be at ease?