The Jubokko — 樹木子, literally 'tree child' — is one of the most disturbing yokai in the Japanese catalogue, and one of the youngest. It first appears in Shigeru Mizuki's 20th-century yokai encyclopaedias, drawn from older battlefield superstitions and given a single, perfect, terrible name.
The story goes like this. Wherever a battle had been fought so fiercely that the ground was soaked in blood — Sekigahara, the burnt fields of the Sengoku wars, the long-forgotten skirmishes of the mountains — an ordinary tree could change. Its roots, sunk for years into corpse-fed earth, slowly took on the taste. Its bark darkened. Its branches, in time, narrowed at the tips into hollow needles. And the tree, no longer satisfied with rain and groundwater, began to need blood to live.
A Jubokko looks, from a distance, like any other tree on the old battlefield. It is only when a traveller stops beneath it — to rest, to shelter from the rain — that the branches move. The needle-tips drop, sink into skin, and drain the unlucky walker dry. The tree, freshly fed, looks healthier than its neighbours for weeks. The bones at its roots are never quite covered by leaves.
Like the Hangman Tree, the Jubokko is a yokai that explains a real thing: why old battlefields feel wrong. Why one particular tree on a moor seems greener than it should be. Why the locals avoid a certain wood at dusk. In the Shinto worldview, places hold what happens to them — and a place that has held that much violence has to put it somewhere.
Mizuki added a small, eerie detail: a Jubokko can be killed only by cutting it down completely, and the wood, when burned, gives off a faint smell of iron. Wear the Jubokko and you wear the darkest of the Japanese tree-yokai — the quiet, well-fed witness that grew up out of what people did to each other and never quite stopped drinking.