Fujiwara no Mokou

Species: Human
Abilities: Eternal youth and immortality, resistance to and manipulation of fire
Occupation: Rescues lost people, Bamboo forest guide, Claims to run a yakitori stand
Location: Somewhere in the Bamboo Forest of the Lost

Formerly an ordinary human, Mokou became an immortal being after drinking the Hourai Elixir about 1300 years ago. Now she is never able to die, though she still feels the pain of injuries as normal. She's considered to be very powerful because she has lived for many years and earned that power, and because she doesn't die and can therefore keep fighting until she can no longer stand the pain. She has hated Kaguya ever since the moon princess humiliated Mokou's father by turning down his marriage proposal after he failed her trial of the Impossible Requests. Though the slight happened over a thousand years ago, she continues to detest Kaguya, knowing full well that she can never get her revenge--nor can Kaguya ever put a permanent end to her. When not fighting with Kaguya, though, she aids the nearby villagers by exterminating youkai and will even guide them safely to Eientei for medical treatment. She is a loner by nature and chooses not to socialize with humans or youkai, and has a dubious personality that can easily switch from friendly to threatening and back again, but her actions seem to indicate she may be a good person. Considering Mokou's surname and her back story as a daughter of an aristocrat charmed by the Kaguya-hime of legend, she is supposed to be the daughter of Kuramochi no Miko (車持皇子), who was given the quest for the Jeweled Branch of Hourai by Kaguya. His model is speculated to be Fujiwara no Fuhito, the factual founder of the Fujiwara clan, a powerful clan of regents during the 9th to 13th centuries. Mokou is one of the few people in all of Gensokyo to wear pants. This, along with her somewhat forceful way of speaking, often leads to her being depicted as something of a tomboy (perhaps why her parents kept her out of public view). However, because conditions in Gensokyo still resemble those of feudal Japan, pants are hard to come by and must be made by a skilled tailor or imported from the outside world, and presumably are much more expensive than skirts. This may make pants a status symbol, and given Mokou's status as a daughter of the old Japanese aristocracy and her rugged lifestyle, it is likely it would be only natural for her to insist on wearing them.

(Source: Touhou Wiki)