Weirdness Spreads, I'm a Strange Object Hunter in the Apocalypse

Sun Hang regains consciousness in a hospital after a strange object attack incident that leaves him with severe brain trauma and complete amnesia. A doctor and nurse inform him that his surgery was successful, but his memory is temporarily lost. A female official from the Investigation Bureau soon arrives and delivers the grim news: Sun Hang incurred a medical debt of nearly four million yuan, and since he has no citizen status or identity records—no DNA match in the database, no tax or insurance records—he is classified as an undocumented person. He is given a choice: sign an employment contract as a temporary investigator to work off the debt, or remain detained. With no other option, he signs, receiving a temporary citizen ID and a temporary investigator certificate numbered 0420. The official tells him he is in the frontline city of Tianfu City and that all expenses of his treatment are his debt. During his three-day confinement in the hospital room, Sun Hang briefly experiences a strange phenomenon: he wishes for warm light, and the lights flicker and the whole room goes dark. He wonders if he caused it, but the sharp pain in his head returns, and he cannot replicate the effect, leaving him uncertain. His requests for internet access are denied, and he is effectively a prisoner. When discharged, soldiers escort him to the Tianfu City Anomaly Investigation Bureau for induction training. The training is minimal: a lecturer explains the classification system for strange objects, dividing them into categories based on Heavenly Stems and Earthly Branches—Jia for rule-based, Yi for phenomena, Bing, Ding, and Wu for biological types (animals, plants, microorganisms), and complex categories for inanimate and hybrid objects. Danger levels range from E to Zero, with Zero-level objects known as "Primal Strange Objects" such as Ding Zero·Decaying Mother Tree, which are absolute taboos. The lecturer abruptly declares the recruits qualified investigators, ignoring their protests about the lack of practical training. They are told that specific mission intelligence will be provided with assignments, that experience is useless against strange objects, and that no weapons will be issued—fire support comes from accompanying soldiers. Each temporary investigator receives a single dormitory room, a smartphone with restricted internet access, and a booklet of outdated information on known strange objects. Soon after, Sun Hang receives an email with his first mission: investigate the abandoned amusement park in South City, where sixteen young women have gone missing in the past month, and a police intern named Hu Lijun vanished during a reconnaissance. The mission difficulty is provisionally rated E-class. He is grouped with two other temporary investigators he met during training: 0398, a young woman, and 0401, a man. The mission details reveal that the disappearances cluster around the amusement park, and there are reports of robed individuals and possible rituals. 0398, realizing she fits the victim profile, attempts to escape but is quickly caught and fitted with tracking collars and anklets. As the three are driven to the amusement park, the driver comments that E-class missions can unpredictably escalate in difficulty, and he wishes them to return whole. Sun Hang and his companions head toward the amusement park, fully aware of the dangers but left with no alternative except to complete missions to clear their debts and eventually gain citizenship.