Translation: small ball mouse
Habitat: mountains in northeastern Japan
Appearance: Kodama nezumi are tiny creatures which resemble spherical dormice. They inhabit mountain forests in the Tōhoku region.
Behavior: Kodama nezumi are rarely encountered due to their remote habitat. However, they do have one particularly notable behavior. When the mountain gods grow angry, kodama nezumi begin to swell. Internal pressure builds up. They inflate like a balloon. Then suddenly, they rupture down the spine and burst. The sound of this explosion is said to be louder than a gunshot. Everything nearby is splattered with their flesh, blood, and innards.
Origin: Kodama nezumi are attested to by the Matagi, an ethnic group of hunters who live in the mountains of northeastern Japan. They believe that kodama nezumi are messenger animals sent by mountain gods. A kodama nezumi explosion is a warning that the gods are angry. When Matagi hunters hear this sound, they immediately stop their hunt and return home.
Anyone foolish enough to continue hunting after hearing a kodama nezumi explosion will have a poor catch. Worse, they invite the wrath of the mountain gods. They might get injured or even meet with disaster, such as being buried in an avalanche.
Some Matagi believe that kodama nezumi are the reincarnated souls of hunters and foresters who defied the wrath of the mountain gods.
Legends: One cold winter night, some hunters were resting in a mountain hut when to their surprise a woman came to the door. She begged them for shelter for the night. However, the mountains were sacred. Women were forbidden from entering them. And so the hunters had no choice but to turned her away.
The woman continued wandering until she came upon another hut. Once again begged the hunters inside to give her shelter for the night. These hunters also knew the law, but they took pity on the woman. It was too dangerous to roam the mountains at night, so they allowed her stay.
When morning came, the woman had vanished. The hunters who allowed her to stay had a successful hunt. Nobody was injured, and they all returned to their village laden with rich game. In fact, the woman was actually a mountain goddess, and she had blessed their hunt.
The group of hunters who turned her away, however, met a different fate. Instead of a blessing, they received her wrath. She transformed every one of them into kodama nezumi, and they were never seen again.