The Kojiki describes it the way a surveyor would. Eight heads and eight tails on one body. Eyes the colour of the winter-cherry lantern-plant. Moss growing on its back, with cedars and cypresses standing up out of it as though the animal were a hillside. A length covering eight valleys and eight ridges. And underneath, along the whole belly, a raw and permanently bleeding surface.
Almost nothing else in Japanese myth is described in this much physical detail, and every element of the description has been read as evidence for what the thing originally was.
A river with eight branches
The most durable interpretation makes it a watercourse. The serpent lives in the upper reaches of the Hi river in Izumo — a real river, now the Hii, which drains into Lake Shinji in Shimane. It comes down once a year, as a flood does. Its body spreads across the valleys the way a braided river spreads across a plain. Its back is wooded because the levees and gravel bars of a Japanese river are wooded. And its belly bleeds because the Hii runs red.
That last detail is not poetic. The Izumo region was one of Japan's great centres of tatara ironmaking, a technology that extracted iron from ironsand by charcoal smelting in clay furnaces, and which required stripping riverside hillsides and sluicing enormous volumes of sediment to concentrate the sand. The runoff turned the water rust-coloured and choked the channels, and the resulting flooding was severe enough that the practice was periodically regulated. A red river that floods annually and yields iron from its bed, defeated by a hero who pulls a sword out of it, is a fairly economical account of the whole story.
None of that is stated in the sources. It is inference from the geography of a region the Izumo Fudoki describes in detail, and it is inference most Japanese scholarship treats as sound.
The girls, and the eighth daughter
The frame is a sacrifice narrative. An elderly couple, both of them earthly kami, have had eight daughters, and seven have been taken in seven successive years. Susanoo, newly exiled from heaven, arrives beside the river, sees a chopstick floating past, deduces that people live upstream, and finds them weeping over the last one.
The annual tribute of a girl to a water-monster is a story shape found across Eurasia — Andromeda and Perseus, George and the dragon, the Chinese river-marriage tales — and it is worth being precise about what makes this version distinctive. The rescuer does not fight the creature in single combat. He engineers a solution: a fence, eight gates, eight vats of repeatedly refined sake, and eight heads that cannot resist them. He wins by knowing what the thing wants.
He also transforms the girl, Kushinada-hime, into a comb and puts her in his hair before he starts, which is either protection or an unusually literal way of keeping her close. Her name contains the element for rice paddy, which supports reading her as the fields the flood took every year.
What was in the tail
Cutting the fourth tail, his blade chips. Inside is a sword, which the Kojiki calls Ame-no-Murakumo, the gathering clouds of heaven, and which he sends up to Amaterasu as a conciliatory gift. It later acquires the name Kusanagi and becomes one of the three imperial regalia.
The direction of the transfer is worth noticing. The single most important weapon in Japanese myth comes out of a monster in Izumo and travels to the imperial line, rather than the other way round. For a chronicle whose purpose was to establish the throne's legitimacy, that is a substantial concession, and it belongs with the wider accommodation of Izumo that runs through the Kojiki.
Eight, and what it is doing
The number eight recurs to the point of insistence: heads, tails, valleys, ridges, daughters, gates, vats. In early Japanese, eight functions as a conventional expression for "many" rather than a count — the same usage gives the eight hundred myriad kami and the eightfold fence of Susanoo's poem. Reading the serpent as having a precise anatomy misses that its dimensions are a way of saying enormous.
There is a second reading, less securely grounded, that takes the eight heads as eight tributary streams and thus makes the arithmetic geographic after all. Both can be true; the number is doing rhetorical work and topographic work at once.
Where it is remembered
The Izumo region keeps the story physically. Yaegaki Shrine near Matsue enshrines Susanoo and Kushinada-hime and is now overwhelmingly visited by people praying about relationships. Susa Shrine, Suga Shrine and a scatter of sites along the Hii claim locations from the narrative. The Izumo Fudoki — a regional gazetteer independent of the two chronicles — preserves its own related material and place-name legends.
Above all it is danced. Iwami kagura, the vigorous popular kagura of western Shimane, performs Orochi as its signature piece, with the serpent represented by long articulated cloth-and-bamboo bodies operated by dancers inside them, sometimes eight of them filling a stage, wheeling around a Susanoo who fights them one at a time. It is loud, late-night, extremely popular, and it is how most people in the region actually know the story.
Every JRPG's final boss
The eight-headed serpent may be the most reused monster in Japanese games. Final Fantasy, Megami Tensei, Ōkami, Nioh, Yu-Gi-Oh!, Smite and a long tail of gacha titles all field a version, generally as a late-game multi-headed dragon fought in a river or a shrine. Ōkami stages the sake trick faithfully enough that players learn the actual method. Neon Genesis Evangelion and Blue Eyes-style card designs borrow the silhouette without the story.
The consistent adaptation choice is to make it a fight. In the source it is a trap, and the hero's virtue is preparation rather than strength — which is not what a boss battle wants.
Is it a dragon or a snake?
The word used is orochi, an old term for a large serpent, and the creature described has no wings, no legs and no ability to fly or breathe fire. It is emphatically a snake, and the Chinese-derived dragon that Japanese art later adopted — the four-clawed, whiskered ryū of temple ceilings and dragon-palace tales — is a separate import with a separate iconography. Modern illustrations routinely draw the serpent as a dragon because that is what the audience expects, which quietly erases a real distinction between an indigenous river-snake tradition and a continental one. The dragons and serpents survey sets the two families side by side.
Why is the sake described in such technical detail?
Because the text specifies yashiori no sake — sake brewed by repeated refinement, the mash strained and re-fermented multiple times to raise the strength — and that is a real, documented brewing method rather than a decorative flourish. Its presence dates the story's telling to a period when high-strength sake was a notable product, and it ties the episode to Izumo's other industries alongside the ironworking. It also supplies the mechanism: ordinary sake would not incapacitate the creature, and the narrative needs a plausible reason why eight heads would drink themselves insensible. The chronicles are generally vague about how things are made; here they are not, and the exception is informative.