A sea squirt is an animal. It fixes itself to a rock and stays there for the rest of its life. It is orange, and lumpy, and the shape has earned it the name sea pineapple, which is the friendliest thing anybody says about its appearance.

They are farmed along the Sanriku coast, and summer is the season. They are eaten raw, grilled, deep-fried; for this dish they are cut open, chilled, and dressed with vinegar, and nothing is cooked at all.

Sweet, salt, bitter, sour and savoury: it is said to carry all five of them at once, which almost nothing else does. Not in sequence, the way a complicated dish reveals itself, but simultaneously, in a single mouthful, so that a first-time eater cannot separate them and often cannot say afterwards what it tasted of.

A fresh one hardly smells at all, which surprises people who have been warned about it. But it deteriorates very fast, and as it goes the smell that develops is usually described as metallic, or like petrol. People divide sharply over this food, and the division probably has less to do with taste than with how many hours had passed between the water and the plate on the day they first tried it.