After the death of the protagonist Zhang Mo, when he was queuing up to be reincarnated in the underworld, he was stopped by the judge because he had "357 obsessive express deliveries" that were not completed during his lifetime. He was forced to become a "courier in the underworld", responsible for delivering the unfulfilled wishes (obsessions) of the deceased souls to the recipients in the underworld in the form of "express delivery". In the process of delivering the mail, he gradually discovered his past life identity - "Siyou", the top administrator of the underworld communication system, and was involved in a confrontation with the evil organization "Postal Breaking Society" aiming to cut off the communication between Yin and Yang. The core tension of the story lies in the protagonist's growth from a ghost who was forced to work to a "siyou" who shoulders the heavy responsibility of rebuilding the communication order in the underworld.
