This is a double-sided world hidden under the neon lights of contemporary cities. Skyscrapers are erected and subways are running smoothly. In a corner that is not illuminated by light, there is a mysterious organization called the "Absence Bureau", under which there is a very special group of people, who are collectively called "echo dealers".
The existence of echo quotient began with a failed experiment. Lin Huilan, the former chief scientist of the "Neural Link" project, privately developed a semi-finished AI chip in order to save her best friend Hu Yuanyuan's vegetative husband. This chip called "Qiankun" requires extreme human emotions - greed, anger, ignorance, pride, and suspicion, the "five poisons" - as nutrients to be activated. Once activated, its function has already exceeded Lin Huilan's original imagination: it can not only repair damaged brain nerves, but can even read, map and even trade human consciousness and memory.
Hu Yuanyuan was the first responder. She woke up her husband Li Songnian, but opened an unknown door with her own hands. In the following ten years, the Qiankun system was secretly copied, improved, and circulated on the black market. More and more desperate people are willing to use their stories and emotions in exchange for a conversation with the deceased, a forgetfulness, a revenge, or a humble chance of redemption.
The Bureau of Identification named this phenomenon the "echo phenomenon" and called the operator an "echo dealer." They are both maintainers of order and sources of danger. All stories ultimately point to a taboo existence sealed at the bottom of the Qiankun system - "Wanxiang Taoist". He is the true creator of the first-generation Qiankun system and the original source of all Lin Huilan's research results.
