"Attack, my UFOs! Shoot those lowly humans out of the sky!" The things flying in the air may have looked like your stereotypical flying saucers, but they were, in fact, fragments of the holy and mythical Flying Storehouse whose true form had been hidden. This is the story of an incident where a treasure ship and UFOs filled the skies above Gensokyo. An incident that definitely didn't proceed as it should have.

"Incidents" and "disturbances" are the names given to the many unnatural and mysterious events that cause a fuss in Gensokyo. This incident was meant to end a long time ago. But why is that? Time only flows in one direction, with no going back, so who can say what should or shouldn't have happened? Only those who are aware of the existence of parallel worlds can properly theorize about the what-ifs.

Incidents can be made to last longer by making the incident more difficult or even temporarily impossible to resolve. Such incidents are called Prolonged Incidents. The cause of the incident itself and the prolonging are separate, so it is usually safe to assume that there are two different culprits. According to the trustworthy records, the Treasure Ship Disturbance was peacefully resolved when the youkai monk who was sealed away in Makai talked (and had a battle of bullets) with the humans who unwittingly helped set her free. Nue Houjuu tried to disrupt the efforts of both parties but this conflict was eventually resolved too. That is what should have happened.

EX Beings are beings capable of causing Prolonged Incidents, and the specific set of circumstances present in a world that facilitate the manifestation of EX Beings is called the EX Factor. However, while these beings are capable of causing Prolonged Incidents, that does not necessarily mean that every EX Being in every world has done so. In other words, if an incident has been prolonged, EX Beings would be the prime suspects, and even if they didn't cause that specific prolonging, they could very well have caused a different Prolonged Incident in another world. Also, it's important to note that the EX stands for Extended, not Extra. More research is currently being conducted to determine the exact nature of the EX Factor.

Nue Houjuu is an unidentified youkai. However, "nue" is also a name given to many different types of scary youkai, most of which were reportedly seen during the Heian era (794 to 1185). So, presumably, Nue Houjuu is also a type of nue. It's also probably safe to assume that she is an exceptionally powerful youkai since youkai are spiritual beings that gain strength from their infamy and the terror their name inspires. Like many of the youkai in Gensokyo, Nue loves to do her own thing, play pranks, and have fun, but she is also an embodiment of the mysterious and unidentifiable nature of youkai. Nue Houjuu is suspected of causing the Prolonged Incident. She certainly has the means. But what about the motive? Does she impede attempts to resolve the incident simply for the fun of it? Would Nue truly wish for the incident to last forever?