This infographic comes from the Association of Paranormal Study, and is a great little piece on a very interesting creature from Japanese folklore, the Akaname!
A couple of years ago, my son really got into Yokai Watch---a cute cartoon starring adorable characters depicting a variety of real Japanese ghosts and monsters, also known as Yokai. As part of his summer study that year, we studied Japanese culture and REAL stories of yokai, which was perfect for me, because I got to read and learn about a ton of quite interesting (and sometimes spooky) creatures myself. However, I don't remember coming across the Akaname...
The name, Akaname, literally translates into filth licker. Akaname, sometimes depicted as being red in color, is said to sneak into old bathhouses and dilapidated homes at night with its super long tongue to lick the bathrooms clean of all the gross grime and yuck that tends to build up in such places. Its origins in popular culture can be traced back at least as far as Toriyama Sekien's 1776 publication, the Gazu Hyakki Yagyō ( aka, "The Illustrated Night Parade of a Hundred Demons" ).
Personally, I would LOVE to wake up to a perfectly clean bathroom, despite the nauseating idea that someone or something LICKED it that way. However, the Japanese people were, on the whole, not so inclined. Seeing a yokai, any yokai, was generally considered to be a creepy experience. Added to that, cleanliness is extremely important in Japanese culture, and I'm sure it was a great dishonor to have a demonic creature have to come in and lick away your filth. So, people would ensure that their bathing spaces were spic and span before they went to bed each evening.
Another interesting aspect of the akaname that I found was the idea that this creature focused less on literal filth (mildew, dirt, etc.) and more on the metaphor of filth as a moral impurity. In other words, keep your dirty thoughts and actions out of the bathroom, lol!
*Want MORE Japanese Legends from Theresa's Haunted History of the Tri-State? Check out this article on the Onamazu, the Earthquake-Causing-Giant-Catfish!*