Modern corporate drone Lu Changgeng dies from overwork and transmigrates into the Great Qian Dynasty, where demon disasters run rampant. On the brink of death, he binds the Lifespan Longevity System. Starting as a lowly constable in borderland Baiyun County, he slays a century-old fox demon and quells a corpse tide from the mass graves. His hardcore combat prowess makes him stand out, and he is recruited by the Qingzhou Demon Suppression Bureau. He forms a human-demon covenant with the demoness Yun Meng, who is coerced by the Azure Wolf King. Inspector Captain Shen Yanqiu of the Demon Suppression Bureau first obsessively believes Lu Changgeng is in league with demons, guarding against him and clashing with him at every turn. But after repeatedly witnessing his integrity and sense of duty, she gradually grows to admire and love him. A female disciple of the Nanyang Sect follows at his side. Ultimately, atop the walls of Qingzhou City, he uses the Prison-Suppressing Golden Body to slay the thousand-year-old Azure Wolf King and win the Battle to Defend Qingzhou.