(Request given to me by ShurunaAteisuto) Inside the gallery of caverns that the underground is, a single door is left with many mysteries. Indeed, nobody ever came out of the door after entering, bringing the curiosity of many youkais hiding with it. So far, nothing ever escaped once they entered, leaving nothing but wonders. A new soul brought there by simple curiosity soon stepped through the door. Koishi Komeiji, who only discovered the access inside the walls by pure coincidence, entered the forbidden door. Inside, she was met with quite a surprising encounter. ...An encounter that may prove to be fatal to her.

Reimu Hakurei, the Shrine Maiden of Gensokyo, was entrusted by Yukari to uphold and preserve the balance, resolving incidents whensoever they occurred. But that trust was bound to be broken at some point, as the old saying goes "You either die a hero or live long enough to see yourself become the villain."