Ten years ago, modern civilization was devastated by ancient beasts. With help from the Xuanwu lineage, humanity clung to a slender hope of survival and built the "Heavenly Crystal" along the borders of its territories to keep ancient creatures from invading.
The ancient creatures that forever roam beyond the crystalline barrier still covet modern civilization, and a small number of demons have ultimately managed to infiltrate human cities.
They move strangely, hiding in the darkness. Relying on their bloodline instincts, they evade human surveillance while constantly hunting unsuspecting people.
One rainy night, high school student Sui Bian was targeted by a pair of bloodthirsty eyes lurking in the darkness...