On the banks of mountain streams throughout Japan, you can hear the "shoki shoki" sounds of the elusive Azuki-arai, or Azuki (Red Bean) Washer, as he washes his azuki beans. Sometimes he can be heard singing:
"Azuki togo ka, hito totte kuo ka, shoki shoki"
(Shall I wash my azuki beans, or should I snatch a person to eat? Shoki shoki"
Despite its morbid song, the Azuki-arai is a very shy spirit whose only mischief is surprising humans with the sound of his washing and song. When a curious person approaches, he can be heard diving into the water to escape.
(As an aside, this is my absolute favorite yokai and I have no idea why.)