In a world shrouded in eternal darkness, where the sun and moon no longer shine, a deadly fog has spread across the land, claiming lives and plunging the world into despair.  The 'poison fog' hides the truth of a curse that lingers from the wrath of the People King, and with only gray mornings and black nights, the people train their youth to face the veil monsters born of the darkness and army of devils borns.  Among those nightwalker a girl by the name of Sky Logen, determined to protect her family. she battles the horrors lurking outside the city, as she herself becomes a part of old ancient devil make her fate intertwined with the very creatures she was trained to destroy.  Now, she must unravel the secrets behind the fog and the curse before it consumes her and all she holds dear.