Meng Yao, a top modern strategy student, transmigrates into a novel as Chu Yue, the "demon concubine." To avoid death, she gains the indulgence of the sickly emperor, investigates the late emperor’s case, allies to fight villains, returns to modern times after solving the crisis at the Longevity Banquet, and finally meets a boy with a gear-shaped birthmark on the grassland.