"The difference between damnation and celebration is paper-thin. At the same time, Takatsuki and Naoya learn of the urban legend about 'Library Marie'. Apparently if you solve a hidden cipher in the library collection, you'll be cursed. 'The unlucky letter and cursed cipher.'

Upon investigating the legend of a demon god in a village, in a grotto they find a skull with a hole in it. Soon after, Takatsuki is plagued by unexpected suffering. How will Naoya help him out of this one?!"