Despite it being midsummer, the seasons in various locations are completely out of whack. The Hakurei Shrine is showered in cherry petals, the Youkai Mountain is basking in the middle of autumn, and the Forest of Magic is blanketed in snow... and thanks to some strange force, Gensokyo's fairies are running rampant with unfathomable strength. In the midst of this undeniable incident, the girls set out to investigate and find the perpetrator behind it.