| SPOILER WARNING!!
Yukiyasha (Snow Demon) is the main antagonist of Nuriko's Light Novel, Yukiyasha Den, and also the central plot device. According to local legend, the demon comes down from the top of Goddess Peak at the end of each full moon for its sacrifice. Historically, the Yukigase villagers offer the most beautiful virgin in exchange for guaranteed safety.
In the novel, there were many strange occurrences in the village. The howling in the mountains, the dead livestock, and butchered travelers were suspected to be Yukiyasha's doing. In reality, it was the Seiryuu Warrior, Ashitare.
But Yukiyasha was still present in the story. After hundreds of years of tormenting the villagers, the demon wanted to become a human when her cruel existence started to take its toll. She restrained herself from consuming any sort of meat for one hundred years and stopped appearing before the villagers. Her disappearance also caused the snow to stop falling in Yukigase. When her demonic powers were fully sedated, she took human form and returned to the village to right all the wrongs she had done. She was found by Sojun Cho, Nuriko's uncle, and took on the name: Fuyoh. The two were later married and got pregnant.
Unfortunately, Fuyoh's vegetarian diet had to change for the pregnancy and it awakened her powers, causing it to snow for the first time in one hundred years when Nuriko arrived. With Ashitare lurking in the mountains and (unknowingly) mimicking Yukiyasha's demonic behavior, Fuyoh found it hard to suppress her demon blood any longer. She turned into her true form and escaped into the mountains. Nuriko followed and tried to reason with her, determined to reach Fuyoh, but to no avail. A battle ensued and after Byakuren sacrificed herself to save Nuriko, Fuyoh saw what she had become and ran into the crumbling mountain, never to be seen again.