Hana-ingen is the scarlet runner bean. It reached Japan at the end of the Edo period, and because the flower is large and striking it was planted to be looked at, not eaten. Eating it began at the Sapporo Agricultural College in the Meiji years, and serious cultivation only from the Taisho era.

It wants cold. In a warm place it will flower and then set nothing, which restricts where it can be grown to a short list of provinces. In Gunma that means Nakanojo, Tsumagoi, Kusatsu, and Naganohara, at elevations between nine hundred and thirteen hundred meters.

The beans are startlingly large, a single one about the size of a thumb.

Because they are dried for storage, the only way to make them edible is to cook them soft, and the method is patient rather than clever. Soak overnight. Boil in plenty of water, let it cool, change the water, boil again, and repeat that two or three times before finally simmering them with sugar and salt until the sweetness is in. They appear at festivals, at weddings and funerals, in the new year boxes. Some households set the harvested beans on the household shrine before anyone eats any of them, which is not something people do with an ordinary crop.