The yugao is not a morning glory, despite the shared half of the name. Nor is it the maru-yugao from which kanpyo is made. It is the naga-yugao, long and shaped something like a gourd. The name comes from the flower opening in the evening, in contrast to the asagao that opens at dawn.

It has been grown along the northern foot of Fuji since the Taisho period, and cultivation aimed at the market rather than the household picked up from around 1965. In Yamanakako village it is generally called yugo rather than yugao.

The soup made from it is about as simple as a soup can reasonably be.

Stock is drawn from dried sardines. The yugao is cut into thin slices or into cubes and dropped in. Once it comes to the boil the miso goes in and the pot comes straight off the heat. Cooked, the flesh turns translucent in the bowl, and what it leaves in the mouth is a particular slippery softness that no other vegetable grown here gives you. It is eaten in August and September, in the heat. It is made into other things as well, but the miso soup is what the district returns to. The fruit of a flower that opens at dusk, eaten at the hottest point of the year.