In a world showered by God's light, the shadows cast upon hell are ever darker. In those shadows, lie the Sins. After a heated battle, Gwendolyn Von Alysstar, a Holy Paladine, finds herself possessed by a Sin, Sitri, prince of the Fire Throne. Together, they search for a way to break this curse, all the while avoiding the suspicious gazes from both the Church and the Sin Kings. However, before they discover how to break up their bond, they first need to discover how to coexist.