This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Yosuzume (Japanese)
Yosuzume ("Night-Sparrow") are bird yokai, the knowledge of which are handed down within the Hada District, Aichi Prefecture towns of Tanokuchi, Tomiyama, in Kitagawa, Aki District, in Minamiuwa District, Ehime Prefecture, and in other places. As indicated by their name, they are a yokai that appear in the night and chirp "chi, chi, chi" like a sparrow, and are said to pass in front of people who walk along mountain trails.
In Kitagawa, Aki District, they were not a bird, but were also said to be a black butterfly, and while chirping "cha, cha", they would go inside purses and umbrellas, and it would become impossible not to walk along noisily, but they are said to disappear upon relaxing one's ki. Likewise in Ehime, they were regarded as a kind of moth, and if one experienced one before a mountain dog shows up, they would come flying to the extent that it would not be possible to walk forward on the path.