I Traveled Through Time and Became a Policeman, and the System Gave Me the Magic Ability to Kill Monsters.

In the middle of the night, the county government prison was broken into, and the demon rats were rampant! Young detective Chen Jiuyuan was bleeding on the spot, and saw his stunning colleague dying. When he was about to die, the [Demon Martial System] was activated! "The starting reward is the Qingxin Pill, the supreme skill "The Secret of Immortality", and the peerless sword skill "The Flowing Cloud Sword Technique"!" The injury healed instantly, and the magical power was at hand! Chen Jiuyuan used his backhand sword to kill the demon rat. The demon element filled his body, and his strength soared! However, before he could take a breath, a terrifying roar could be heard from deep inside the prison: "Whoever kills my heir, die!" A larger rat king stepped out of the shadows, its demonic aura rising to the sky!