Youkai (妖怪, "mystic apparition" or "mysterious calamity") is a term used to refer to Japanese folk creatures and ghosts, or to supernatural beings in general. Because there are thousands of stories of magical beings around the world, the different types of youkai are endless.
The term youkai is sometimes used interchangeably with obake (お化け, roughly "one that takes on a form"), meaning things which have undergone some kind of supernatural change, beings with shapeshifting powers, or phantoms and ghosts. It is a common Japanese belief that after a certain amount of time, ordinary objects and animals gain life and personality, becoming a kind of youkai. In some cases even a normal human can become a youkai under the right conditions or vice versa.
Youkai in Touhou
The growth of rationalism and new explanations for strange phenomena has made it difficult for youkai to survive in the modern era - the valley of Gensokyo, sealed off from the Outside World by the Great Hakurei Barrier in 1885, serves as one of their few sanctuaries. Some youkai, such as Mamizou Futatsuiwa and possibly Shou Toramaru, have managed to survive in the outside world for many years, although both have since moved to Gensokyo for unrelated reasons. Yukari Yakumo is speculated by some residents of Gensokyo to be a youkai of the outside world who merely comes to Gensokyo to play, but this is just one of many rumors about her.
Since Gensokyo's human population is relatively small, but youkai are dependent on conflict with humans in order to survive, its inhabitants have developed a number of unique rules and customs. Among other things youkai are forbidden from killing natives of the Human Village (but not humans from the Outside World, even if they find themselves in Gensokyo), and inhabitants of the Human Village are forbidden from turning themselves into youkai. More recently the Spell Card rules were created as a system of formal duels which de-emphasize raw power, limiting the damage that can be caused by youkai and making it easier for humans to resolve youkai incidents. While the Hakurei shrine maiden is officially in charge of exterminating youkai whenever they cause trouble, these "exterminations" (along with those of her colleagues) are usually nonlethal, with sealing or execution reserved only for youkai that cannot abide by the rules.
Youkai are primarily spiritual beings rather than physical ones. As such they are more vulnerable to faith-based attacks (such as charms, wards, etc.) than to physical injuries and ailments; it's said a youkai can even recover from being cut into pieces, if the damage has insufficient "meaning" behind it. Some youkai, such as magicians, have bodies more similar to humans and may lack this ability.
Related to this, most youkai keep their promises once given. While a human who loses a Spell Card duel can immediately challenge the winner to another, youkai rarely do so.
Many youkai are stronger and longer-lived than humans, with lifespans reaching into hundreds of years or more. Marisa claims that Rinnosuke Morichika, who is only half-youkai, has not visibly aged since she was a child. Unlike fairies, however, they are not immortal.
All youkai have an innate connection to the Moon - according to Yukari Yakumo it was the moon's dim light which gave birth to the youkai by causing humanity to fear and create legends about them, while Kaguya Houraisan claims that some earthlings were turned into monsters by Lunarian's to regulate the earth's "filth".
Over time many of Gensokyo's youkai have come to take on human traits and vice versa. Youkai with human-like bodies and/or personalities have become far more common, even among normally monstrous species. However, even the most human-like youkai would still be considered strange by human standards.
The tengu and kappa have a complex society which lays claim to the upper parts of Youkai Mountain and guards its borders jealously, though it is described by as Ran Yakumo as simply a half-hearted attempt to mimic the Outside World. This society was once led by oni before they migrated to the Underworld. The tengu later formed an alliance with the gods of Moriya Shrine after it was transported to Gensokyo.
Various "hated" species of youkai such as satori, tsuchigumo, and oni are found in the Underworld. A treaty with Gensokyo forbids surface youkai from travelling to the Underworld, in exchange for the Underworld youkai agreeing to contain evil spirits left over from the regions that were once part of Hell. Underworld youkai, however, are free to travel to Gensokyo.
While she does not hold any position of authority, Yukari Yakumo has negotiated many deals and projects including the Great Hakurei Barrier, and arguably has the most influence of any independent youkai.
In Curiosities of Lotus Asia Chapter 18, Rinnosuke Morichika mentions that the Kappa are often mistaken to be related to the Chinese river youkai/god known as a Kahaku. He tells Sakuya Izayoi that while they may have similar names (And presumably similar in many other ways to the point of being identical), they are two completely different creatures. He states that just because there’s a youkai with a similar name in a country in the outside world, to think that they are the same creature is unreasonable.
This is known in science as parallel evolution. This may also be the case of why Oni and Vampires share portions of their name and have identical weaknesses, while they are clearly two different species of youkai. Because modern science is fairly new, similar supernatural creatures may easily be grouped up as the same thing.
Youkai in Seihou
It's never been explicitly stated in the Seihou Project if Youkai do exist in the world of Seihou. However, there are various possible candidates that could be considered to be in this bestiary because of their unusual characteristics in the series, such as: Muse (because she stylises in magic and may either be a god, devil or vampire), Yuitia (because she's a phantom), Vivit and Icarus. Although she's a Touhou Project character, Yuuka Kazami is the only character to be stated as a youkai within the series.
Characters under this Bestiary
While the majority of characters in Touhou are youkai, in most cases they are placed in an explicit subcategory. The following are characters who have been identified only as youkai, with their exact "species" being either unique or unstated.
- Hong Meiling
- Yukari Yakumo
- Yuuka Kazami
- Rinnosuke Morichika (Half-youkai, youkai half unknown)
- Ichirin Kumoi (Possibly a Wanyuudou or Katawa-guruma)
- Saigyou Ayakashi (Cherry blossom tree with youkai-like powers)
- Bakebake(?) (referred to as "monsters" (お化け obake) in Story of Eastern Wonderland's omake text file)
- Evil Eye(?)
- Bewitching Lotus Flower?
Books and articles
- Wikipedia entry for youkai
- Yokai.com, a site listing and describing a large number of youkai.
- hyakumonogatari.com another similar site.
- Forbidden Scrollery chapter 25
- Eastern and Little Nature Deity: Fairy of the Moon
- Cage in Lunatic Runagate: Fifth Chapter. "Under the dim light of the moon, all sorts of things blanket the Earth in shadows, such as grasses, trees, mountains, rocks and buildings. With light as weak as moonlight, it is impossible to eliminate these shadows. And they are the birthplace of humanity's fears, sometimes creating legends of youkai. In a manner of speaking, the moon gave birth to all youkai."
- Imperishable Night: Scarlet Team's Scenario. "The moon gave many powers to beings of the earth. Many of them, such as magic, were originally the moon's power." "We of the moon turned some on the Earth to monsters, to regulate their filthiness..." Although "monster" uses different Japanese characters than what's used for "youkai", Kaguya's latter statement appears to be referring to youkai, as she then comments about how the humans sealed them away (Gensokyo's creation and/or the myriad of other ways that humanity sealed or lost the fear of the youkai).
- Silent Sinner in Blue Chapter 3
- Perfect Memento in Strict Sense