kappa (河童)

Kappa is one of most famous yokai.

Kappa lives in river or around lake.

He does mischief when a person approaches.

He pulls up "sirikodama" from the buttocks of the person.

Japanese I do not know "sirikodama" too.

Probably "sirikodama" is the internal organs.

Top of Kappa's head is plate

and he have a shell such as the tortoise.

and he has a web in hands.