Fourteenth game of the Touhou series, eleventh of the mainstream lineup and ninth of the Windows generation, as well as the sixth of the same generation's mainstream games.
One wintry day, a geyser laden with evil spirits erupted near the Hakurei Shrine. Due to a noninterference agreement between overground and underground youkai, two humans - Hakurei Reimu and Kirisame Marisa, each with an overground youkai to their aid via a magic artifact - were sent underground to investigate, finding the geyser to be a cry for help by a feline creature concerned about her avian friend's sudden change in character and her naive plot to turn Gensokyo into a part of Hell.
