After the protracted world war, the city was full of humans who had undergone mechanized transformation for various reasons. These people were called "expanders". At the same time, the developer of expansion technology, the technology company "Beluan", also expanded rapidly due to the war's demand for high-tech weapons and expansion transformation, and became a giant enterprise that controlled the entire city. With the development of expansion technology, a gap gradually arose between expanders and ordinary humans, and many frictions also emerged. The "excess expanders" who gained powerful power due to excessive transformation began to cause a series of social problems, and qiwan.cc became a major hidden danger threatening social stability. Therefore, the Reconstruction Department under the government established an agency called EMS (Expander Countermeasures Bureau) to manage affairs related to expanders, forming a subtle situation of secret connection and mutual restraint with the dominant Beluan. In the chaotic social order, the protagonist of the story, a surplus expander with a revolver as his head - Qian (qián) Shisan, was active in the city as a "processing house", responsible for accepting commissions and handling various difficult cases related to expanders, so as to live a life walking on the edge of a knife. But this kind of life changed because of a "kidnapping case" with a hidden story...