In 2157 AD, a catastrophe called the "Great Rust" destroyed human civilization. A kind of "siderophilic bacteria" derived from meteorites crazily devoured metals, causing the modern industrial system to completely collapse and human society to return to the agricultural era. The survivors built a "cocoon city" on the ruins and used city walls to isolate themselves from the outside world. But the city is not a pure land - resources are scarce, classes are solidified, and mysterious "rust pattern birthmarks" will appear on the faces of newborns. The deeper the birthmark, the lower the status.
Shen Xiuyi is the "waste ferryman" at the bottom of Cocoon City. He is responsible for transporting industrial waste that cannot be processed in the city to the "Rusty River" outside the city for dumping. He had a large dark brown birthmark on his face and was disliked since he was a child. The only thing he cherished was the half bronze medal given to him by his adoptive father before his death, with the words "Purifier" engraved on it. During a dumping of waste, he rescued a mysterious woman with burns all over her body by the Rusty River. After waking up, the woman stared at his birthmark and said something that shocked him: "This is not a curse, it is a map. The lines on your face point to the truth of the Great Rust."
From then on, Shen Xiuyi was forced to be involved in an adventure that subverted cognition - he wanted to search for the legendary "Purifier" relics and solve the mystery of the birthmark, but on the way he discovered that the top management of Cocoon City had been concealing a shocking secret: the so-called "Great Rust" may not be a natural disaster, but a man-made disaster.
