Yuki-onna are legendary Japanese demons that appear in the winter time and drain the life energy of victims during the most bitter of cold weather, usually through a kiss. In terms of appearance, they take the form of stunningly beautiful women, and with a proper diet of life energy they can retain their youth indefinitely. They are extremely sensitive to the environment around them, and taking them away from Japanese soil or exposing them to hot climates can result in fatal consequences for them. Because of this, they are usually found in the mountainous areas of Japan until the seasons grow colder, at which point they go into the other villages and seek prey.
Although they are commonly associated with succubi, they are actually the prototype for an experiment during the Dark Ages that led to an off-shoot of the succubi race. While most succubi are demons of purely supernatural origin, a cult of alchemists and assassins called "the Black Sun" encountered a Yuki-onna that had found itself on the mainland of what is now known as Russia, and upon capturing her, examined her body and sought to use her abilities as a weapon. The ability to harness the life energy from victims and turn it into destructive energy, as Yuki-onna would using their wintry elemental abilities, was something that the Black Sun hoped to replicate within their ranks to create a new breed of assassins that would shape the world to their liking.
The Yuki-onna predictably died from the Black Sun's mistreatment of her, but they learned enough to begin their experiment. Kidnapping what they deemed to be exceptionally beautiful young women across Europe, the Black Sun infused them with their dark magic to such a sufficient degree that they could no longer consider themselves human. Never again would they age, and the dark magic had enchanced their beauty into that of a true goddess of lust. No longer requiring food and water, the women now possessed an uncontrollable thirst for life energy: energy that could only be drawn through sexual contact with humans.
There was one "succubus" who stood up to her master's, having retained her sanity and humanity while most of her fellow test subjects had gone mad with their overwhelming lust. Upon escaping the Black Sun's grip and saving as many of her fellow test subjects as she could, this lone succubus obtained the notes written on the captured Yuki-onna, and theorized that her own body worked in much the same way.
As such, she told her sisters a way they could escape the dark fate the Black Sun thrust upon them while at the same time satiating their urge for men.The Destined One
Unlike most succubi, Yuki-onna see their urges for a man's life energy as something done out of necessity, and use their seduction abilities to lure a man into her grip with no romantic feelings. However, this does not mean that they are immune to falling in love. A Yuki-onna requires a human man in order to reproduce, and the men who impregnate their icy mistresses are known as "Destined Ones." To Yuki-onna, finding a Destined One means finding their one true love, and she will lose interest in all other targets for the sake of pursuing this one mate.
Black Sun Succubi are largely the same way. When they have found their Destined One, whatever behavior they may have been known for prior to that point becomes glazed with a lovesick haze. It becomes difficult to the succubus to think clearly as they long for their Destined One, fantasizing about what they would be like if she were to one day consummate with them. For succubi and yuki-onna, mating with their Destined One is the equivalent of achieving Nirvana: a satisfying end to their long search for their next meal.
As for the Destined Ones themselves, once visited by their mistress for the first time, they too will be unable to think about anything else but pleasing her, devoting their bodies and minds to her happiness. The connection between them goes beyond simple seduction magic, and is more in line with a deep spiritual connection that can best be described as "love at first sight." Because of this, the chances of a Destined One and his mistress not being mutually attracted to each other is extremely rare.
Since they are ageless, the yuki-onna must ensure that their Destined One retains his youth along with her. To achieve that end, the yuki-onna and Black Sun succubi have a very specific mating ritual to ensure an eternity of love.Stage 1: The Infusion of Life
A human's life energy is channeled through specific points in the human body. In Latin, they are referred to as vis vitae, and they have also been referred to as "chakra points" and "ki points" in Eastern cultures. But what is not known to most humans is that those points in the body can be removed, allowing the human body to create a greater amount of life energy than normal. There are several negative consequences to this, but in order for a Yuki-onna to truly be with her Destined One forever, a risk must be taken.
With a soft kiss on the lips or cheek, the Yuki-onna causes her Destined One's life force points to slowly vanish, forcing his body to create the absolute maximum amount of life energy he can. This results in his belly and chest expanding like a balloon, bringing him just short of bursting point and leaving him completely helpless as his inflated body disables his mobility. Assassins that have mastered this technique have come to call it "the Blowfish Kiss," and use it to either euthanize victims due to the heart eventually giving out, or to burst them violently.
Of course, the Yuki-onna have absolutely no intention on letting either of those things happen. Now that the Destined One's body has produced an endless fountain of life energy, she can begin the next step.Stage 2: The Expulsion of Death
Just as Yuki-onna can remove life force points on her "fiance's" body, she can also add new ones to her. With another kiss, usually on the Destined One's inflated body where the life force surplus is at its most intense, the Yuki-onna can ease the swelling with a kiss-shaped scar that absorbs the excess flow of life energy. Usually it only requires one of these marks to return the Destined One to his original size, but there have been cases where a Yuki-onna can't help but give two or three if her desire for him is intense enough. Within minutes, the Destined One's body has been restored, but the flow of life energy rages within him as heavily as it ever was.
With the new life point on his body regulating the endless well of life energy flowing through him, commonly known only as "the Mark," the Destined One has been granted eternal youth. The Yuki-onna has transformed her Destined One from an ordinary human into the perfect immortal husband that can eternally satisfy and sustain her. Now that their union has been assured, the Yuki-onna and Destined One can give into their love for one another and complete the final stage of the mating ritual.Stage 3: the Binding of Love
At this point, separating from their wife can cause the Destined One great physical and emotional pain, especially if they are around other women without their mistress being immediately present. Because of this, most Destined Ones refuse to leave their Yuki-onna's side, engaging in long bouts of passionate love-making. Naturally, this results in the Yuki-onna becoming pregnant, and as long as they have their Destined One nearby, they can expedite the gestation process.
Immediately after conception, the Destined One often falls into an exhuasted slumber, and gives the Yuki-onna yet another method to sustain herself while at the same time sustaining her unborn child. By projecting her astral form into the Destined One's dreamscape, the Yuki-onna can continue receiving the full extent of her husband's love and life energy. By this stage, the Yuki-onna is now completely enamored with her husband, and becomes lost in her passion to a point where the couple can remain asleep for several months at a time with no ill effects. A full, uninterupted slumber can allow their infants to be born in as little as 3 full months.
Because a Yuki-onna does not awaken her vampiric nature until she reaches physical maturity, the Yuki-onna often leaves her daughter in a human village to be cared for by mortals, though she will keep a close watch on her to make sure that her daughter is not mistreated. Then, once her daughter has reached the proper age, the Yuki-onna appears before her and finishes her training and educates her on her immortal life.
Though it is exceedingly rare, Yuki-onna and Black Sun succubi can give birth to males. Although they are unnaturally handsome as they reach maturity, they are NOT considered incubi as they do not feed on life energy. However, their mothers will treat them with the same love they would a daughter, and often promises their son's hand in marriage to the daughter of another succubus.
At the end of their active lifespan, the yuki-onna and her Destined One will go into seclusion and spend the rest of their unnatural days together. Because succubi consider other members of their race "family," often calling one another "sister," these hives are often shared.
The lone succubus who discovered all of this has but a single goal for her race: all succubi will find their Destined Ones, reach the end of their active lifespans peacefully, and eventually wipe away the dark nature of their origin. This will be their final victory.