KUROKAWA ONSEN, KUMAMOTO >> Rolling mists fill the valley as we descend from Mount Aso to Kurokawa Onsen, a riverside town in the depths of Kumamoto Prefecture.

Twenty minutes outside of Kurokawa Onsen, on the edge of the town of Oguni, is Soba Kaido road, nicknamed for the many noodle shops positioned alongside its course. Our group stops at Kagoan, a 100-year-old farmhouse that has been refurbished as a soba restaurant; its mossy roof and thick wooden beams hint at its age.

From the restaurant’s window, the Baba River can be seen flowing fast and powerful on the other side of a well-kempt garden. Catching our gaze, the waitress tells us that the water is used to make the noodles, mixed with buckwheat flour in proportions that change with weather conditions such as temperature and humidity. The noodles, when they come, are sublime: The earthy taste of buckwheat defines each mouthful, complemented by a rich soy-based soup and a generous side of maitake mushroom tempura, lightly fried in a crisp batter.

Twenty-nine ryokan inns line the Kuro River to make up the bulk of the village. Though it has its roots in the Edo Period (1603-1868), it was not until the 1960s that Kurokawa Onsen became well-known to the public. Historically, it was a rest stop for daimyo lords and travelers as they crossed between the Kyushu towns of Hita and Taketa.

In the latter half of the 20th century, efforts to turn Kurokawa Onsen into a tourist destination resulted in significant expansion. In 1961, just six hotels were open to the public, but this number more than quadrupled as the Kurokawa Onsen Ryokan Association promoted the town’s open-air rotenburo baths.

Despite the growth, the town maintains a charm that effuses throughout the buildings and narrow alleyways that run down the steep banks to the Kuro River. It feels old and has escaped much of the overenthusiastic concrete landscaping present elsewhere in Japan.

By the time we have checked in to Ryokan Sanga, the town has emptied of day visitors, and the streets are deserted but for a few guests of the ryokan, strolling quietly along the river dressed in striped yukata and holding orange umbrellas to protect them from the light drizzle of the evening. The slap of their sandals reverberates, echoing the soft pitter-patter of the rain.

From the town’s information center we buy nyuto tegata, onsen-hopping passes that allow the wearer access to three different outdoor baths at any of the participating ryokan. After visiting onsen at two different inns we are boiled through, faces a deep red and fingers wrinkled and pruned. The cool air provides relief as we wander the town, stopping at Patisserie Roku, to try the shop’s specialty, choux cream pastries, filled with fresh cream to order.

Up the hill from the patisserie, a circular window reveals a bounty of sake: nihonshu, umeshu, shochu, all produced and sold locally. Across the road, a souvenir shop sells trinkets and gifts.

For all the allure of the shops, and the quaint products inside, the real attraction of Kurokawa Onsen is the river, which cascades down from the mountains and defines the town’s architecture, from its riverside baths and elegant bridges to the color of the buildings that are painted black in tribute to the Kurokawa, which translates to “black river.”

As darkness falls, we are treated to tuneful laughter that floats across the river, accompanied by the gentle chatter of people starting their elegant kaiseki (traditional multicourse) suppers.

And after dinner? With few other distractions, there is little to do but bathe again and succumb to sleep.

Kurokawa Onsen is best accessed by car and is approximately a two-hour drive from the city of Fukuoka, north of Kyushu. Public buses to the town are available but run only four times a day, ineffective for day trips, as the last bus returns to Fukuoka at about 4 p.m.