Gu Changsheng, an ordinary modern man, accidentally transmigrates into a fantasy world and becomes a low-ranking trainee demon-slaying guard at the Demon Suppression Platform of the Great Qian Dynasty. After slaying a Peach Blossom Demon at a critical moment, he unlocks the Sinful Codex, a special cheat ability. Every demon he kills grants him a powerful authority-based ability, but he must also inherit the sins and curses left behind by the slain demon. Gu Changsheng only wants to survive in peace and stay away from fighting, yet all kinds of bizarre debuffs keep causing him trouble. When a beast tide attacks the outer city, he is forced to shine and quickly becomes a rising star at the Demon Suppression Platform. Later, he is ordered to infiltrate the Heavenly Music Sect as an undercover agent to investigate a demonic cult's conspiracy. He intends to quietly gather intelligence, but who could have expected...