A bat that lives long enough changes. First it becomes a nobusuma. If it grows older still, it becomes a yamachichi. This creature waits until you are asleep. Then it sucks out your sleeping breath. What happens next depends on someone else in the room.
What does it look like?
The yamachichi comes from one picture book. That book is the Ehon Hyaku Monogatari, also called Tōsanjin Yawa. It was published in 1841 (Tenpō 12). Tōsanjin wrote the text, and Takehara Shunsen drew the pictures. A same-content edition, Ehon Kaidan Zoroe, may be older. So the first printing may come before 1841.
Shunsen's picture shows a creature shaped like a monkey. The folklore writer Tada Katsumi describes it in Gensō Sekai no Jūnin-tachi IV (1990). He points to one more detail. Its mouth sticks out to a point.
The name is written 山地乳. The three characters mean "mountain," "earth" and "milk." Read together, it is yamachichi.
The breath in the night
The book's main text gives the rule. The yamachichi sucks the breath of a person who is asleep. If someone else sees this happen, the victim's life grows longer. If nobody sees it, the victim dies the next day.
The text written inside the picture tells it a little differently. Here, the creature sucks the sleeper's breath first. Then it strikes the person on the chest. The one who is struck dies. But a second person may be sleeping in the same room. If that person wakes up, the victim gains a long life instead.
So in both versions, the sleeper cannot save themselves. Their fate rests on a witness.
Where it lives
The picture text says many yamachichi live in Ōshū. That is the old name for Mutsu Province, today's Tōhoku region in northern Japan. The book adds that it hides deep in the mountains.
The book says that deep in the mountains it is called satori-kai. Tada Katsumi's notes take this to mean it is the same as the Satori. The Satori is a mountain yokai of the Chūbu region, in central Japan.
A book that doubts itself
The Ehon Hyaku Monogatari does something unusual here. After it tells the rule, it steps back. It says that no one has really had their life lengthened this way. No one has really died this way either. Still, the book says, in some places everyone fears it.
Where it comes from
The yokai scholar Murakami Kenji makes a plain point in his Nihon Yōkai Daijiten (2005). The name yamachichi is not found in any other book. It is not found in any folk tradition either. Everything we know comes from the 1841 picture book.
That shapes how to read it. The bat origin may be the book's own idea. If so, the author may have built the creature in steps: bat, then nobusuma, then yamachichi.
The two versions of the rule may also say something. In one, a watcher saves the sleeper. In the other, a waking roommate does. One reading is that the story is about not sleeping alone. That reading is ours. The book does not say it.
The satori-kai name opens one more door. If Tada is right, the yamachichi may be a regional cousin of the Satori. The book gives no more than the name, though.
Go deeper
Books worth owning if this world pulls you in.
- The Book of Yokai →Michael Dylan FosterThe most readable scholarly introduction to yokai — where they come from, what they mean, and the major creatures.
- Japandemonium Illustrated: The Yokai Encyclopedias of Toriyama Sekien →trans. Hiroko Yoda & Matt AltThe complete Edo-period bestiaries that so many of these entries trace back to, in full English translation.
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Yamachichi today
The novelist Kyōgoku Natsuhiko took the creature into modern fiction. He wrote a story called "Yamachichi." It appears in his collection Saki no Kōsetsu Hyaku Monogatari. Like the 1841 book, the collection's title calls itself a hyaku monogatari, a "hundred tales."
