Yūrei

A yūrei is the dead returning with a reason. Where a yokai belongs to a place and troubles whoever passes, a ghost belongs to a person and a motive: a grudge, a debt, a love, a child left behind. The familiar picture is Edo: a woman in the white kimono of the burial, hair loose, hands hanging limp from the wrists, fading away below the knees, often with a pale flame beside her. The footless ghost is usually credited to the eighteenth-century painter Maruyama Ōkyo, and the stage of the nineteenth century fixed the rest.

The line between ghost and yokai is not clean. The funayūrei are drowned sailors who act like a sea yokai; the shichinin-misaki are seven dead travelling together; Oiwa is a ghost with a face as famous as any monster’s. This site files them all under yokai and says in each article what kind of thing it is.