Kusatsu

The springs were known long before the town. Local tradition credits their discovery variously to the monk Gyoki and to Minamoto no Yoritomo, and the name is usually explained as a contraction of kusōzu, "foul-smelling water", for the sulphurous reek that still hangs over the valley. By the medieval period the water had a reputation for healing skin conditions and wounds, and warriors came to recover here.

Under the Tokugawa the town became one of Japan's most famous spas. The ranked lists of hot springs published in the Edo period, laid out like sumo tournament charts, regularly placed Kusatsu at or near the top, and pilgrims, merchants and patients made the long walk over the mountains for a cure that lasted weeks. The water is unusually acidic, which gave it a name for killing almost any ailment, and the yumomi method of cooling it by stirring, rather than adding cold water, was developed to preserve its strength.

In the 1870s and 1880s the German physician Erwin Bälz, who taught medicine in Tokyo, studied the springs and recommended them in European terms, which brought the town into modern medical tourism; a monument to him stands in the centre. A community of people with Hansen's disease formed in the Yunosawa district in the early 20th century and was later moved into a national sanatorium, a difficult chapter now publicly acknowledged. Skiing arrived in the 1910s, buses and roads followed, and Kusatsu settled into its present form: a resort of a few thousand residents receiving millions of visitors a year.

The bath governs the day here. Guests arrive in the afternoon, bathe before dinner, walk the lit streets in the yukata and wooden geta lent by their inn, bathe again before bed and once more after breakfast. The clatter of geta on stone is the town's characteristic sound, along with the wooden boards of the yumomi and the Kusatsu Bushi, the folk song sung to keep time while stirring — its melody is played from loudspeakers and known across Japan.

The free neighbourhood bathhouses are a genuine local institution rather than an attraction: each belongs to a part of the town, is cleaned by the people who use it, and follows unwritten rules about silence, order and cleanliness. Visitors are welcome as long as they behave as residents do. The etiquette of the tub — washing first, never soaping in the water, not adding cold water to a bath another person has tempered — is learnt quickly.

The town keeps a shrine above the hot water field, a temple long linked to cures, and a summer festival in which the water itself is honoured. Since the 1980s a summer classical music academy has brought European teachers and students to the mountains each August, and concerts are held in halls and hotels; the mixture of folk song, steam and chamber music is peculiar to Kusatsu.

About 6,300 people live in Kusatsu, and almost all of them depend on the springs. Inns and hotels, restaurants, sweet makers, bathhouse maintenance, souvenir shops and the ski area account for most employment, and the working year follows the seasons: the snow months and the autumn colour are the peaks, with quieter stretches in late spring and early summer.

The town sits alone in the mountains, a long bus ride from the nearest railway, so residents drive for supermarkets, schooling beyond the local level and hospital care in the valley towns. Winter is hard work — snow clearing, frozen pipes, roads closed by drifts — and the mineral water corrodes metal so persistently that fittings are replaced far more often than elsewhere.

As in much of rural Gunma, the population is ageing and slowly falling, and inns passing to a next generation is a standing worry. Against that, Kusatsu has been unusually successful at drawing visitors, including foreign ones, and the town has spent heavily on the central square, the footpaths and the lighting of the Yubatake. Volcanic alerts at Kusatsu-Shirane, which have closed roads and part of the ski area in recent years, are the other constant of local life, along with the maintenance of the wooden troughs through which the town's livelihood flows.

Kusatsu's best-known food is a sweet. Onsen manju, small steamed buns of wheat flour filled with red bean paste, are made all day along the lanes around the hot water field, and shops push samples on passing visitors in a competition that has been going for generations. Rice crackers, chestnut sweets and soft-serve ice cream fill out the same shopfronts, and the mineral sediment skimmed from the troughs is sold in paper packets as bath powder rather than eaten.

Because this is a mountain town, meals lean on what grows on the slopes. Soba made from local buckwheat, sansai — wild vegetables such as bracken shoots and butterbur — mushrooms in autumn, and Gunma's konnyaku, a firm grey jelly made from a root, appear in almost every kitchen. Freshwater trout and char are grilled whole on skewers, and eggs slow-cooked in the spring water are sold warm by the bag.

The set dinner at a ryokan is the main meal of a stay: a succession of small dishes with local wagyu or pork, a hotpot heated at the table, pickles and rice, served in the room or a dining hall. Gunma is a sake-brewing prefecture, and local brews appear alongside beer and shochu. In the cold months the town's restaurants serve nabe hotpots and the thick noodle stews of the region, eaten after a long soak.