The Fox Sister
A man had three sons and no daughter. He prayed for a daughter, even if she was a fox. His wife gave birth to a daughter, but when the girl was six, one of their cows would die every night. One night, he sent his oldest son to watch. The boy watched, and told him that his sister did it, by pulling the liver out of the cow and eating it. His father accused him of having fallen asleep and having a nightmare, and threw his son out. Next, the second son was sent to watch over the cows, and nothing happened until the moon was full again. Then, the sister struck, and the second son was also thrown out for reporting this. Following this, the youngest son was sent to watch; he claimed that their sister had gone to the outhouse, and that the cows must have died from seeing the moon.
The older brothers wandered until they met a Buddhist monk, who sent them back with three magical bottles: a white one, a blue one, and a red one. Once they arrived, they found their sister living alone; she told them their parents and brother had died, and implored them to stay. Finally, she persuaded them to stay the night and somehow made a rich meal for them. In the night, the older brother was woken by the sounds of chewing. He rolled over, saw the meal, and realized that they had eaten corpses. His sister stood over his dead brother, eating his liver. She told him that she only needed one more to become a human.
He fled, throwing the white bottle behind him, and it became a thicket of thorns. As a fox, she made her way through it. He threw the blue bottle behind him, and trapped her in a river, but as a fox, she swam ashore. He threw the red bottle behind, and she was trapped in fire. It burned her until she was no more than a mosquito.
The folk tale has inspired, among other works, the webcomic The Fox Sister.