Gensou Tansaku Nitroid! is a puzzle and exploration based platformer by the doujin circle Desunoya, the makers of other Touhou fangames such as Marisa and Alice and Guruguru Suika. The game stars Nitori Kawashiro as she explores Gensokyo in pursuit of an escaped "nuclear reactor."
Utsuho Reiuji has been spotted away from her post in the Underground Geyser Center, causing worry to the Moriya Shrine. Nitori has taken it upon herself to investigate the matter for the good of the mountain, and maybe for some personal benefit as well.
