狐火（きつねび）
Kitsunebi
Fox fire: lights without a source on night fields, and the other ghost-lights beside them.
A line of lights moves along a hillside where there is no road, or a single flame hangs over a paddy and goes out when you walk toward it. In most of Japan these were kitsunebi, fox fire, lit by foxes from their own breath or from a bone held in the mouth, and a long line of them was a fox wedding procession passing. Toriyama Sekien drew the lights in 1776 and the wedding in 1779.
Other words cover other lights. Onibi, demon fire, is a cold blue flame near graves; hitodama, a human soul, is the light that leaves a body at death and drifts away; at sea, lights on the water were the lanterns of the drowned. Painters put a pale flame beside every ghost.
Related yokai
Kitsune
狐（きつね）
A 1930 account from Toyooka describes blurred blue or red foxfire moving restlessly from beyond the mountain to somewhere close by.
Funayūrei
船幽霊（ふなゆうれい）
A ruined boat draws alongside at night and its crew asks for a scoop. Give them an ordinary one, and they may use it to fill your boat with seawater.
Chōchin-obake
提灯お化け（ちょうちんおばけ）
One of forty-eight monsters on Yoshimori's print Shinban Bakemono-zukushi is a paper lantern with an eye, a mouth, and something coming out of the mouth. That picture is the record — there is no story attached to it.