Kyōkotsu (狂骨) is also known as crazy bones and feeds off the vengeance of others. It is characterized by a tattered robe with a skull and untameable hair emerging from it. These spirits reside in wells and like to rise up and scare anyone unfortunate enough to be passing by at that time.
This spirit forms from bones that were improperly disposed of down a well. This most often happens with murder or suicide victims but can also be from someone who died from accidentally falling in a well. A huge grudge is formed form the lack of burial and disrespect shown by disposing of the bones down the well and a kyōkotsu takes shape. When it is disturbed, the shiryō rises from the well and curses whoever is passing by and it passes its grudge along.
I don’t know about you guys but I think I’ll avoid walking by any wells just in case! As much as I love Halloween and the spooky season, that absolutely does not transfer into wanting to be cursed by a vengeful spirit.