Cut one open and it is red the whole way through. The colour is not painted on the outside; iron oxide is worked into the paste while it is being made, and it stays evenly distributed through the block. It is not a synthetic dye but a food additive that is, quite literally, iron.

Nobody agrees on why. One account says Oda Nobunaga, who liked a spectacle, ordered it dyed. Another says the merchants of Omi took the idea from the red paper that decorates the floats at the Sagicho festival. A third says it was cut thin and coloured to stand in for sashimi at meals where fish was not allowed.

None of these has a document behind it. That Omihachiman has been making red konjac for a very long time is established. Why it is red is not, and the local accounts of it are guesses arranged after the fact, which everyone involved will tell you quite cheerfully.

It tastes more or less like any other konjac. But one red piece sitting in a bowl of brown simmered vegetables changes the whole look of the dish, and it is difficult to go back to the ordinary kind afterwards. Something has continued for centuries without anybody being able to say why. Colour alone appears to be enough.