According to Japanese beliefs, Yamajijii look like eldery men about 3-4 feet tall, with only one leg and one eye. In actuality, they have two eyes, but one of them is so huge and the other so tiny that they appear to have only one eye. Their bodies are covered in fine gray hair, and they can be found wearing old clothes, tattered rags, or nothing at all. Their teeth are sharp and very powerful — a yamajijii’s bite is said to be strong enough to crush the bones of wild boars or monkeys.

Yamajijii live in the mountains far from human settlements. They rarely appear before humans, but their tracks are easily recognizable. They leave deep, sunken footprints about 12 inches long every 6 to 7 feet (from their hopping about on one leg). Because their bite is so strong, hunters would sometimes tame yamajijii and use them to drive away wolves. They also have the uncanny ability to read peoples’ thoughts as they think of them. They are most well known, however, for their powerful voices. The cry of a yamajijii is so powerful it blows the leaves off of branches, splits trees and moves rocks, reverberates through the mountains, and shakes the heavens and the earth. They enjoy shouting contests, and will occasionally allow a human to challenge them; however, humans who are close to a yamajijii when it shouts sometimes have their eardrums burst, or even die.

A legend from Shikoku tells of a brave hunter who challenged a yamajijii to a shouting contest. On the hunter’s turn, he fired his rifle when he shouted, winning the contest. Later, the yamajijii realized he had been tricked, shape-shifted into a spider, and sneaked into the hunter’s bed to attack him in his sleep.

In some versions of the tale, the clever hunter prepares for the shouting contest by praying to the gods of Ise and crafting a special holy bullet inscribed with their names. This bullet had a very special power: when fired it would never miss its target. Because of its magic, whenever the hunter carried it with him it would invariably attract the attention of yokai; however, any time a yamajijii came near enough to threaten him, the hunter would display the bullet, and the yamajijii would flee in terror.

A tale from Tokushima tells of a group of woodcutters warming themselves by a fire in a cabin when yamajijii suddenly appeared to them. The woodcutters were terrified and all thought of the same idea: kill the yokai! The yamajijii read each one of their minds one by one and learned of their thoughts, when suddenly one of the logs in the fire split with a loud snap! The yamajijii thought that there must be a mind he could not read among the hunters, and he quickly fled the cabin in terror.

A story from Kochi tells of a kind yamajijii who gave a sorghum seed to a poor farmer as a gift. The farmer sowed the seed and that year was blessed with an incredible harvest. That winter, the yamajijii returned and asked for some mochi to eat. The grateful farmer gladly gave the yamajijii as much mochi as it could eat. The next year another great harvest followed, and again the yamajijii came back in the winter to ask for mochi. Each year, the yamajijii was able to eat more and more mochi, until it was able to eat 3 huge barrels-full. The farmer became afraid of losing his fortune, and gave the yamajijii a pile of burned stones, passing them off as yaki-mochi. The yamajijii ate them, but soon began to feel sick and hot. The farmer offered a cup of hot oil, passing it off as tea, but the yamajijii realized the farmer’s trick. Surprised and hurt, it fled into the woods, but died before it could get back to its home. Afterwards, the farmer’s family fell into ruin and was never rich again.