Have you ever found a cut on your body, and have no idea where it came from?

Though this phenomenon is universally relatable, it’s particularly prevalent in the northern Honsho regions of Japan. Residents of these mountainous areas have experienced shallow, painless, cuts appearing on their body, usually appearing around the thigh, calf, or ankle.

It’s so common; at one point it even gained international attention under the title of “Spontaneous Wounds”.

The winters in these northern regions of Japan are wildly unpredictable; huge temperature fluctuations can create sudden whirlwinds and strong gusts of wind.

Riding within these fierce winds, moving so fact they can’t be seen is the Kamaitachi.

They look like a normal weasels, except for the long, sharp blades attached to their front and back legs. Even though they look deadly, the cuts from a Kamaitachi are fairly shallow and nonlethal.

Some stories say these creatures travel in three’s, riding the wind and looking for travelers. When a person is attacked, the first weasel cuts him, the second licks up his blood, and the third applies a healing ointment – resulting in a painless shallow cut.

These “spontaneous wounds” also appear in areas covered by clothing. So it’s believed some versions of the sickle weasels doesn’t travel on the wind, but are completely invisible.

All of these stories may be derived from the Itachi, a shape-shifting weasel with similar powers to the Kitsune, and Tanuki. A common theme in Japanese folklore is when an animal (or object) reaches a certain age, usually over 100 years; they gain powers and become a Yokai.

Like other stories of shape-shifting creatures, weasels are most often seen as tricksters. With their agility and sharp senses, they perfectly fit the archetype.

The Kamaitachi was depicted in woodblock prints as early as 1776, in Toriyama Sekien’s collection titled Illustrated Demon Horde’s Night Parade. So stories describing the sickle weasel have been around for hundreds of years.