Ame onna are a class of yokai that appear on rainy days and nights. They summon rain wherever they go, and are blamed for kidnapping and spiriting away children. They appear as depraved, haggish women, soaked with rainwater. They lick the rain off of their hands and arms like wild animals.
Ame onna are related to minor rain deities. Unlike the gods, however, ame onna are not benevolent. Though the rains they bring might save a village in drought or bring fortune to farmers, they have a more sinister purpose—under the cover of the rain, ame onna wander the villages looking for newborn girls. If they should find a child born that night, they snatch it and carry it off into the darkness, spiriting it away to another world.
Mothers who have their babies snatched away sometimes transform into ame onna themselves, out of grief and despair. Having lost their minds, these transformed women roam the streets at night with large sacks hoping to replace what was stolen. They sneak into houses where crying children can be heard, and steal them away from their homes into the night.
Ame onna go back to the ancient folk religions of Japan and China. The rains were said to be brought by benevolent gods and goddesses who lived as clouds by morning and as rain by night, forever traveling between heaven and earth. Legend has it that some of these rain-bringing goddesses became corrupted and devolved into evil yokai. They abandoned their divinity to live among mortals and prey upon them.