Osamu and Youko Sonoyama want more than anything to adopt every child from Soramame House, but the wealthy couple can only pick one due to their increasingly old age. While they contemplate this delicate decision, one child's alluring beauty and gentle soul instantly draw them in. Two months later, the Sonoyamas welcome 13-year-old Hitori into their warm and loving home. However, Hitori's humble and overly polite exterior is merely a masquerade. In reality, Hitori is a carefully crafted character played by identical twins Migi and Dali. For them, being the ideal child of this kind couple is merely a stepping stone to infiltrating a certain quiet town. While dutifully protecting their cover, the twins work toward their true objective: to discover the truth behind a past incident that left them with a burning desire for vengeance.

The attempt to capture the mysterious perpetrator who possesses people ends tragically: Lu Guang is rushed to the hospital in a critical state, while Cheng Xiaoshi is arrested for the alleged crime. In light of recent events, the father of Liu Min unleashes his skilled, ruthless lawyer—Qian Jin—after Police Chief Li Xiao, who is spearheading the investigation related to the photo studio owned by Qiao Ling. It appears that no one is safe from the unpredictable and fatal attacks of the adversary who painstakingly hides their identity. As he tries to learn from his past mistakes, Cheng Xiaoshi must act swiftly and decisively to put an end to this devastating trail of death.

Gesicht, an android police detective of Europol, is tasked with finding the murderer of Montblanc, a retired war hero robot. Although it appears that only a robot could have committed this crime, the murder of a renowned robot rights activist casts doubts on the criminal's identity. Indeed, outside of an isolated and unexplained incident that occurred eight years ago, robots are programmed to be unable to kill human beings. However, the lack of human evidence on the crime scene and the similarity of modus operandi lead Gesicht to suspect that the two murderers might be the same being—be they man or robot. Shortly after Montblanc's passing, another retired elite war robot is mysteriously eliminated. Gesicht notices a pattern in the choice of murder victim: both dead robots belonged to a group of the seven most powerful war machines ever designed. Determined to stop the murderer from eliminating the five remaining veterans, Gesicht seeks help from Atom, a cutting-edge android who resembles a human boy. The duo must now hunt down the rogue killer before the series of murders is carried on, lest the very fabric of society suffer irremediable damage.

The fourth season of Shaonian Ge Xing.