I'm a bit leery to straying toooooooooo far from Dresden canon however. The simplest (perhaps too simple) way to make things match up would be, like you say, making ying and yang match up with winter and summer and sticking everything else into wildfae.
Yeah, I wonder at what point it becomes a completely different fictional world just using the Dresden Files rules. That's not a bad thing if it's a stand-alone campaign, but for those playing a more conventional DF campaign it would be better to keep basic similarities.
Speaking of Wildfae, the Center/Yellow Dragon is an interesting entity that could help focus the theme of the five elements and directions. The Center is rather like a Spring and Autumn Court in the dual Summer-Winter system. If you go by yin and yang the balance that the Center represents is even more important, since neither yin nor yang is the ideal by itself--rather, the balance is critical. (Which was kind of the entire point of Summer Knight, when you think about it.)
The Yellow Dragon as neutral arbiter could be the one that's keeping the Yin and Yang Courts from a state of constant conflict. If the Yellow Dragon went missing, however, the two Courts may have difficulty containing hostilities or maintaining balance. The reason behind the recent severe snowstorms, perhaps?
Especially with the rampant faking of genealogical records after the end of the 양반 (yangban) as an organized class so that everyone and their dog could claim to have 양반 ancestry.
Yeah, no one knows whether they really are of noble blood or our ancestor was an enterprising commoner who bought/stole a name. 양반 outnumbered the commoners by the end of the Chosun period anyway, because many who were actually of noble blood were selling their name to make money and those commoners who could afford a noble name wanted the yangban's immunity from forced state labor. Factor in the confusion of the fall of Chosun and the Korean war, and it's really hard for anyone to know their actual ancestry.
Sort of like the 화랑 reborn then? They have a cool Arthurian vibe that could fit in just fine.
The Hwarang (화랑) were warrior nobles who swore allegiance to the king, so I suppose they're largely equivalent to a European medieval king's knightly vassals. Hwarang as an institution lasted for hundreds of years and not all Hwarang were heroic figures, but yeah, the idea of some of the bigger heroes coming back is an interesting idea.
Get iron spikes and drive them into every important place all over the world.
Coolness! Thus the knowledge of the supernatural didn't just fade, but was actively suppressed along with the power of the supernatural. An additional campaign premise might be that this is the reason that predatory supernaturals like the vamps thrived in secret--not only did humanity start ignoring the paranormal, but (mostly) benevolent entities like guardian spirits or land gods largely faded away.
Speaking of the recovery of magic, the Korean government and private groups alike have been active in removing these spikes for the past decades. That, in campaign terms, could help bring about the reemergence of magical beings like the god-beasts (신수) and the birth of magical talents.
On the subject of magical talents, I'll extend the original post into an important area where a Korean campaign is different:
Korean magical talentsAn important point of consideration in a Korean campaign is the forms that magical talents may take. These may be very different from the European or American conception of a wizard. The traditional Korean concept of a supernatural mortal is less "wheezy wizard" and more "supernatural warrior" or "religious practitioner." Some of the archetypes are outlined below, and may be useful for NPCs or PCs.
Gods/shapeshifters: I'm not sure what other tradition to place these under, so I'll start with the old gods in the founding myths. They themselves are not strictly mortal, but they are also the ancestors of the ancient kings whose bloodline is dispersed widely in the population by now. Some of their specific powers, or just general supernatural talents, may show up unexpectely in modern characters.
Some of these beings were from the heavens, as in the case of Hwan-ung (환웅) or Haemosu (해모수). They both showed shapeshifting powers, as when Hwan-ung helped a bear become human and later changed into human form to marry her. Haemosu, who seems to be a sun god, had a shapeshifting battle with 하백 (Habaek, The River Chief). When Habaek became a carp, Haemosu became an otter to catch him; when Habaek became a deer, Haemosu turned into a wolf; when Habaek became a pheasant, Haemosu became a hawk.
Then there are the river gods, like the abovementioned Habaek, another shapeshifter. This line of gods was joined to the sky-gods' line after Haemosu married Habaek's daughter, Yuwha (유화, Willow-Flower). She was then abandoned by Haemosu and cast out by her father, and subsequently impregnated by a ray of sunlight that followed her around (another reason to think Haemosu was a sun god). She gave birth to the first in a line of hero kings, the legendary archer Jumong (주몽). Well actually she didn't give birth to a baby, she lay a huge egg out of which came the baby.
Another set of demigods-become-kings are babies dropped off by the heavens. In both stories, they were found when horses wept at where they were hidden, possibly indicating a horse totem tribe connection. Both have a connection to sky and water. One was found after ritual prayer to the heavens, the other had their location indicated by a ray of sunlight. One was a baby in the form of a golden frog, another was a baby in an egg inside a well.
Some suggestions for using these myths include shapeshifting abilities, perhaps limited to a specific animal like a bear or horse, an affinity to water including the help of water creatures, and shafts of sunlight as unexpected guides. And maybe incredible martial prowess because hey, why not? It seems to be the number one perk of divine ancestry.
Shamans and the shamanistic tradition: Shamanism is arguably the oldest extant religious tradition in Korea. The central figure in shamanism is the shaman (무당). A wizard of the White Council would probably call her an ectomancer, and a character like Mortimer Lindquist would probably feel right at home talking shop with her. These are mostly women, and the talent is thought to pass through the bloodline, often mother to daughter (enforcing the canon idea, incidentally, that magic passes through the distaff line). It may lie dormant for generations before it springs up on an unsuspecting person, usually young and female.
There is a great amount of cultural ambivalence surrounding the shaman. On the one hand, her services are much sought out for those who want good luck in their endeavors, are haunted by ghosts, or want a glimpse into the future. On the other hand, being a shaman is not considered a respectable occupation at all, and being struck with the talent is most often seen as a personal disaster that the budding shaman and her family will try to resist.
The first manifestation of the talent is illness, called 신병 (spirit sickness) or 무병 (shaman sickness). The afflicted, often a young girl or young woman, may experience symptoms including constant thirst, food refusal, social avoidance, and visual (ghosts and spirits) and auditory (cymbals, voices) hallucination. She may also suddenly rush out of the house dancing wildly then fainting in an ecstatic state, and could start giving premonitions, or oracles. These conditions have been observed in Central Asia and Siberia as well.
The sickness is not cured by medicine or by the usual shamanistic rituals (such as 푸닥거리) but only with a special ritual of advent (called 내림굿) where the shaman's guiding spirit is invited to possess her. After she is thus cured, the shaman in training (called 애기무당, or baby shaman) will be trained by her spirit mother (신어머니, 신모, whom the shaman might casually call 신엄마, or "spirit mom") to be a full shaman.
A shaman's primary responsibility is to help the living and dead communicate. In her capacity as fortune-teller she passes on her spirit's glimpse into the future, and as an exorcist she drives out the malignant spirits from a place with rituals (called 굿) involving dance and music. As priestess she brings peace to the dead and prays to the spirits for good fortune in her clients' endeavors.
There's an interesting video showcasing some of the different shamanistic rituals
here. You can see a male shaman talking there, too. Male shamans, called 박수, are very much in existence and I'm guessing they go through much the same process as their female counterparts. I know one of my dad's friends is one, though I never had the chance to talk to him. There's also a freaky part where a shaman is walking barefoot on the cutting edge of a fodder-chopper and she's WALKING BAREFOOT ON THAT FREAKING GIANT BLADE starting at about 1:40. Man, that stuff still weirds me out.
I don't know if these shamans would be invited to join the White Council. From the Council's point of view most are probably closer to focused practitioners or minor talents, and other shamans might not be interested in the foreigners' funny business. Shamans tend to be traditionalists, like most religious leaders, though younger shamans might be more open-minded. But as the Council itself isn't the pinnacle of open-mindedness, the two groups are likely to steer clear of each other for the most part. That doesn't preclude cooperation, and individual shamans may well choose to join the Council.
Taoism: Taoist influence is perhaps best seen in the many 도사 (dosa) figures in Korean literature and popular imagination. Dosa are basically mortals who, through training and meditation, took on supernatural powers and long lifespans. Some may be of the "guardian of the forest" variety, popularly visualized in the form of old men with long white beards (산신령). Other dosa are accomplished martial artists, armed or unarmed. Some common abilities for dosa include shapeshifting, near-teleportation (moving great distances in a short time), flying, and illusions. They may be the closest thing to the Dresden File conception of magical practitioners, and the added martial element can make them very interesting and useful.
Many characters in popular fiction skirt the border between mundane martial arts and supernatural powers. The most powerful martial artists may have gotten their skills by practicing not just punches and kicks, but the skill of controlling their 기 (ki), or life force. Armed martial artists might also have the added advantage of a mystical or spirit-possessed weapon. A whole genre of fiction, called 무협, is devoted to these almost-supernatural martial artists who might or might not be dosa, but do use varying levels of supernatural forces to power their prowess.
Buddhism: Buddhist temples are most often found deep in the hills. Some are a part of well-established tourist or hiking routes, and others might be really out of the way. They will often have the kind of holy aura that repels the nastier supernatural creatures. Individual monks may have supernatural powers such as banishment or exorcism, and there are Buddist rituals that persuade a ghost to let go of its emotional attachments and follow the light to the next world. Reciting holy texts like 금강경, 아미타경, 천수경 and so on may soothe a ghost of its obsessions. In the late sixteenth century, during the Japanese invasion of Chosun, a number of Buddist monks (called 의승병, voluntary priest-soldiers) rose up to defend the country, acting as independent militia or as adjuncts to government forces. A modern monk might be an inheritor of that martial tradition.
Christianity: Churches are usually located wherever people live, especially in big cities. In a city like Seoul Protestant churches (교회) are extremely numerous, from big megachurches to smaller outfits that might take up less than a floor of rented space. Catholic churches (성당) are less numerous, but each is typically a building of its own.
As Bosh mentioned, hardline Protestants can be pretty intolerant toward other religions, and probably all supernatural phenomena that they don't see as divinely inspired. Catholics are generally more tolerant, though there is obviously a wide variety in individual attitudes. Individual ministers or priests, based on the strength of their faith and/or preexisting talent, could have supernatural power. Churches administered by sympathetic holy men could serve as safe houses and sanctuaries, much as in the original novels.
Also as Bosh said, much of the educated urban class is Protestant and pretty conservative to boot. Adventures that involve the supernatural activities of the elite could well involve some snooping around churches. It could be interesting if these rich megachurches aren't actually holy places at all, but that really depends on what kind of social commentary you're willing to introduce into play.