Ippon-datara and "the Last Twentieth" — A Yokai for One Day a Year

The most interesting thing about the Ippon-datara is that it's a yokai story and, at the same time, a calendar rule: "don't go into the mountains on this day." It's said to appear on a mountain pass only on December 20. Put another way, if you just avoid that one day, you'll never meet it. It sounds like a scary tale, but it may really have been a very practical piece of advice for keeping people safe.

This time, we'll start from the stories of Obamine Pass, deep in the mountains of Nara Prefecture, and look at the curious rule of "only one day a year."

A promise: stay out of the mountains that day

December 20 is called "Hate no Hatsuka," roughly "the Last Twentieth" of the year. In some areas, mainly in the Kinki region around Kyoto, Osaka and Nara, it is said to have been an unlucky day when people held back from going out or working in the mountains. Right in the busy end-of-year season, a day for doing nothing was deliberately set aside.

At Obamine Pass, people are said to have told each other that anyone crossing on that day would meet the one-legged spirit. Rather than explaining the reasons, "the Ippon-datara comes out that day" was a far easier message for children and travelers to remember.

Days of taboo like this exist all over Japan. In some places there's a saying that you mustn't enter the forest on a certain day because the mountain god is counting the trees. Setting aside days when no one goes into the mountains also meant creating days of rest, and it's thought to have been a bit of wisdom for not pushing your luck in the dangerous winter mountains.

Free for just one day

Obamine Pass also has a legend about where the Ippon-datara came from.

Long ago, the story goes, a huge wild boar lived in the mountains. After it was shot by a hunter, its spirit became a one-legged creature that attacked travelers. A Buddhist priest sealed the spirit away to help the people, but in exchange, a promise was made: on the Last Twentieth, and only then, it would be free.

What's interesting here is that the yokai is never fully defeated. People can't drive it away completely, so they settle things by agreeing on a date. It looks as if humans and the strange things of the mountains are sharing out their territory. Read this way, "one day a year" is less a sign of terror than a kind of truce.

Where did the single leg come from?

Besides being told of as one-legged, the Ippon-datara is also said to be pictured with a single eye. The "tatara" in its name is the same word used for tatara ironworking, an old Japanese method of making iron by pumping air into a furnace with large bellows.

From this, folklorists have suggested that ironworkers and smiths may lie behind the one-eyed, one-legged yokai: workers who damaged an eye from staring into the fire, or a leg from working the bellows with their feet year after year. There is also a line of thought that links smithing with one-eyed gods. Awe and respect for the people who made iron deep in the mountains may overlap with the shape of this yokai.

There are other one-legged yokai too. The Karakasa-obake, the haunted umbrella, is famous for hopping around on one leg, which we touched on in our Karakasa-obake story. They come from completely different places, but a single leg seems to have been a sign that something didn't belong to this world.

What a one-day yokai leaves behind

For the rest of the year, the Ippon-datara does almost nothing. But thanks to that one day, people had a moment at the end of every year to step back from the mountains and pause.

Tales of single footprints in the snow belong to the same family as the "find the trace before the creature" legends we introduced in our Daidarabotchi story. When December 20 comes around, spare a thought for this dutiful yokai that quietly kept mountain life safe. You can also find Obamine Pass on the Yokai Map.