Aaaah, I'm behind.

This is the Furaribi, a birdlike creatures wreathed in flame and found mostly on the riverside. They are harmless since they mostly just float about, but their origins are fairly sad. In Japan, when a person dies there are ceremonies that must be maintained, even years after the death. If they are not kept or if even one of these are missed, then a soul may become lost, and they may become a furaribi, unable to rest.