Kuroi Yuki (a Touhou LostWord original) refers to black snow. The Netherworld's snow has been stained black by death. Yuyuko is strong against Water Phase (spirits of the dead) and Earth Phase (resurrection).

The ability of Yuyuko Saigyouji (D8) from Multiverse Trail 9 (a Touhou LW original). Unlike the abilities of other Yuyukos, this Yuyuko's ability is shrouded in mystery. Fate is a continuous chain of lives. From life to afterlife, from life to death to life again through reincarnation. Spirits await reincarnation in the Netherworld as lives yet to be born. However, the number of humans in the world keeps increasing. There were far fewer in the past. Does this mean that the total number of souls has also increased? Do souls split somewhere along the path of reincarnation? Maybe, but this could also be explained by the idea of Universal Reincarnation. However, there is one more possible explanation. Imagine, if you will, a set of butterfly specimens... The following report was found in a notebook in Hakugyokurou's library, sitting next to the book that mentioned Fujimi's daughter. Huaxu, a land far to the northwest. A natural land ruled by no one, whose people want for nothing and live extraordinarily long lives. It's a utopia, a land of dreams, and this is why "going to play in Huaxu" is an idiom meaning to "take a nap." It's said that the great Fuxi's mother was from Huaxu. So, is that what this place was? Was this Huaxu? "When all is said and done, the place where I feel most at home has to be Hakugyokurou." This is as far as Yuyuko could go. There was nothing beyond this. She was surrounded by broken things, dead things, things that someone deems to be garbage. That's all there was. They were heaped on a speck of land infinitesimally small. Not even the images in the heavens or the occurrences on earth were spared. The laws governing the position and motion of the Sun, Moon, and stars were lost. The cosmos ran out of batteries. It wasn't bright. Nor was it completely dark because nothing followed a set path anymore, not even photons. Yuyuko built, or rather, rebuilt, Hakugyokurou there. She missed it so much that she was willing to spend the last few traces of order within her to do it. She also thought it would be good to have a home, since she didn't know how long she'd have to stay there... No, that's not quite true. She could guess. She'd probably never leave this place. There was nowhere else to go, after all. There wasn't even a sun. This place was short on data. And so was Yuyuko―she was suffering from data deficiency. That's why she looked so tiny. She had lost some of her temperament, maturity, memories, and even her fate. The reason for this seemed obvious. She expended them as fuel to make multiple leaps between parallel worlds. She could think of no other reason why she'd choose to lose such precious data... unless, of course, that reason itself had also been lost. "First, let's imagine that there's a set of butterfly specimens here." Yuyuko had no one to talk to, but she spoke out loud anyway. She felt that it helped keep her at least somewhat sane. The words from her mouth reached her ears, allowing her to appreciate their meaning. Since Yuyuko is a ghost, she had long since forgotten whether her ears and mouth actually fulfilled any purpose, but surely the same could be achieved somehow even if she lost them. Perhaps that's what was happening now. "A set of butterflies all sharing the same pattern, ordered from smallest to biggest. I find myself picturing each one as it must have lived. They're so well preserved that they look like they could fly off at any moment. The thin, fragile wings are covered in strangely charming scales of shifting hue. It's almost as if the collection paints a picture of a single butterfly's growth, of its journey through life..." When did she start thinking about such things as life, death, and growing old? Yuyuko had always been a ghost who loved dance and poetry, a ghost who indulged in beautiful fragrances and yummy food. But now she almost sounded like a human... "However, if you look closely, you will soon see through the lie." A lie, in other words, a fabrication. But isn't everyone a fabrication? How can a fabrication prove that they truly exist? "Butterflies start as larvae, build a chrysalis, then emerge as an imago. Larvae lack exoskeletons, so they don't make good specimens, but this also means they grow each and every day. Imagos, on the other hand, barely grow at all. They can't outgrow the exoskeleton that encases them." Then what are these specimens that seem to depict a single butterfly in different stages of growth? "They are different butterflies, different individuals, preserved at their moment of death." Is there any way to prove that you're the same person you were yesterday? What about an hour ago, or even five seconds? They are all different yous preserved at their moment of death along the trail of fate... Yuyuko's only option was to die. To die in this place where only the possibility of Huaxu remained. As she waited for death, she thought of Youmu and of her friend who used to hibernate. Would she ever sleep again? Maybe if she had a nap, they could meet again here... in Huaxu.