Even a prosperous world that has long been in existence can come to an end.

Heading towards the hospital to visit her grandmother, ordinary high school girl Takatsuka Azusa gets enticed by a mysterious voice, and ends up in a parallel world much like the Taishou Era through space-time travel.

The Imperial Capital, Tokyo.
It is a city in which new culture and ideologies, as well as old traditions, coexist with one another. In recent years, strange-looking beings dubbed as "Onryou" ran rampant. The Imperial Army formed an elite squad known as the "Onryou Subjugation Organisation", and maintained public order on a daily basis. However, the imperial capital's disorder continued to worsen. Amidst the growing numbers of the public circulating their fears and predictions of the ending of the world, Ryuujin's oracle was finally granted to them. Ryuujin's shrine maiden was then sought to be summoned.

In accordance to ceremony held by the Imperial Army, the one whom was summoned was none other than Azusa. However, not long after she alighted upon the parallel world, Azusa was invited and lead by a mysterious young man called "Darius" to go to the "Enchanted Forest", located to the west of the imperial capital. The young man freely admitted to being a demon, and sheltered her in his estate.

"Come, Miss Shrine Maiden of Ryuujin. Welcome to the dwelling of the demons."

The Imperial Army and the family of demons...

The two sides...

Azusa finds herself getting entangled within their dispute.

[Translation of the official website plot summary.]