Set in a world where gods, monsters and the underworld exist alongside modern city life, Darker by Four follows Rui, an exorcist in training and Yiran, the powerless heir to a powerful magical family.

When a spell gone wrong transfers Rui's powers to Yiran, their lives become dangerously entwined and the pair are drawn into a high stakes conspiracy. Bound by stolen power, fate and uneasy alliances, they must work together to stop the barrier between the living world and Hell from collapsing.