It all started on a dark and stormy night. Remilia was enjoying her night as usual in the Scarlet Devil Mansion, when she suddenly had a house guest in the form of the Youkai of Darkness Rumia. Finding out that Rumia had nowhere else to escape the storm, she allowed Rumia to stay at the Scarlet Devil Mansion, but she was quickly finding that the blond haired Youkai was a mystery. Yet Rumia soon became like a sister the Scarlet sisters.

Waking up in a strange place is never a good feeling - this is what happens to Kushoko Sakai one evening after praying at an abandoned shrine. When she tries to find out where she's wound up, she discovers a world full of Youkai - demons and spirits that prey on humans. What's worse, there seems to be something even more sinister beneath the surface... A Touhou fan story.

The Hakurei Border is finally starting to wear out after centuries of standing. But no one, not even the protectors of the border themselves, know how to repair it; maybe except for one gap youkai. But, the problem is, said youkai has been missing for over 2000 years and not a living person in Gensokyo know where she may be. What to do now? Fortunately, thanks to the efforts of a certain charismatic vampire and the information from a gluttonous ghost mistress, the newly recruited heroes are sent out on a journey to find the youkai and save their beloved world. And where will they start, you ask? Well, none other than in the time when said youkai was last seen: the Era of the Great Games.