Onibi

[1] According to the Wakan Sansai Zue written in the Edo period, it was a blue light like a pine torchlight, and several onibi would gather together, and humans who come close would have their spirit sucked out.

Since they frequently appear during days of rain, even though the "bi" (fire) is in its name, they have been surmised to be different from simply the flames of combustion, and is a different type of luminescent body.

The character 燐 at that time in China could also mean the luminescence of fireflies, triboelectricity, and was not a word that indicated the chemical element "phosphorus".

[1] Meanwhile, in Japan, according to the explanation in the "Wakan Sansai Zue", for humans, horses, and cattle die in battle and stain the ground with blood, the onibi are what their spirits turn into after several years and months.

[17] It has also been pointed out that for the lights that would appear far in the middle of darkness, that if they are able to move by suggestion, then there is a possibility that they could simply be related to optical illusion phenomena.

[1] Furthermore, they are frequently confused with hitodama and kitsunebi, and as there are many different theories to explain them, and since the true nature of these onibi is unknown, there is no real clear distinction between them.