Kitsune (狐) is the Japanese word for fox. Foxes are a common subject of Japanese folklore. Stories depict them as intelligent beings and as possessing magical abilities that increase with their age and wisdom. Foremost among these is the ability to assume human form. While some folktales speak of kitsune employing this ability to trick others—as foxes in folklore often do—other stories portray them as faithful guardians, friends, lovers, and wives. Kitsunebi (狐火) is a kaika (atmospheric ghost lights and fires of unknown origin similar to the will-o’-wisp) told about in legends all across Japan outside Okinawa Prefecture. As its name implies, it has a close relation to kitsune (foxes), and there are many theories stating that the glow of the sigh or long breaths of a fox, other than that it is also said that a fox is knocking together its tail and causing a fire, or that it is the glow from a ball that the fox possesses called the kitsunebi-dama (kitsunebi ball).