On a remote island far from the mainland that's shrouded in darkness, there are two gates that connect to the Realm of the Dead. One of the gates, Higammon, is guarded by humans. The other gate, Kogammon, is watched over by demons. Although each gate is safeguarded, an ancient tragedy has led to a deep rift between the humans and demons. However, after an usual event suddenly occurs at the two gates, the protagonist must go and face the demons. Under influence by the demons, their fate and the island's mystery begins to unravel. And, two hearts will connect and become bound to one another. Thus, a tale colored by fate and the forbidden shall be told.