Kill the Demon and Gain Longevity

In the thirty-seventh year of the Great Qianjinghe Period of the Wei Dynasty, the dynasty was at the end of its rope and its strength was almost exhausted. There are continuous snowstorms in the north, endless floods in the south, hunger and death everywhere in the Central Plains, and refugees everywhere. The yin and yang of the heaven and earth are out of balance, and hostility breeds. Demons and monsters in the deep mountains, ancient forests, and deep pools and cold abyss appear one after another. They feed on human flesh and live souls as wages, turning the Daqian territory into a bloody hunting ground. The imperial court set up the Demon Division to slay demons, but the treasury was empty, the armaments were depleted, and there were only a handful of high-level monks who could barely hold on to the state capital. Countless counties and towns were turned into demon lairs, and the people were living in precarious conditions, living in fear. Shen Yi, an ordinary demon-suppressing officer in Boyun County, was accidentally bound to the "Monster Killing to Borrow Life" system - by killing monsters, you can plunder longevity to extend your life, and you can also use longevity to deduce martial arts and achieve breakthroughs in cultivation. In troubled times, longevity is life, and strength is confidence. In order to protect himself and protect the common people, Shen Yi took a knife into the mountains and forests to kill demons, take away life span, practice martial arts, and break through realms. From the horror of the demon lair in Black Wind Mountain to the phantoms of the misty swamp, he worked step by step, using a mortal body and borrowing the life of demons to find his own way to suppress demons in this end-of-law era where demons are rampant. When the secret of longevity is gradually revealed, and when stronger demons come one after another, can Shen Yi single-handedly maintain peace and even reverse the decline of the dynasty?