The story takes place at the end of an imaginary ancient dynasty, when a mysterious plague called "Corruption" suddenly broke out. The infected person will completely lose their mind within three days and turn into a bloodthirsty and violent "epidemic ghost" with supernormal strength and speed, but degraded intelligence. The real source of the plague was a biochemical weapon secretly developed by the imperial court in order to eradicate dissidents, but the experiment went out of control and spread across the country. On the surface, the court organized a rescue, but secretly it wanted to take this opportunity to reshuffle the power structure.
