Sekizenkan (Kashoutei & Sansou)

Sekizenkan has operated in the mountain valley of Shima Onsen since 1694, positioning it among the oldest continuously functioning ryokans in Japan. Its two upper wings, Sansou and Kashoutei, occupy the forested hillside above the Shima River with 26 rooms between them, connected by tunnels and staircases to the rest of the property and to four distinct bathing facilities shared across the entire estate.

The centrepiece of those facilities is Genroku no Yu, a 1930 Taisho Romanesque bathhouse where arched windows and bare stone columns frame five low tubs set in a row. Sodium-calcium chloride sulfate water flows kakenagashi directly through the floor of each basin at 900 litres per minute, rising from the source without recirculation or treatment. The mineral composition of Shima's spring has been documented since the Edo period as particularly useful for stomach ailments and skin conditions, and was historically sought out after the stronger, more acidic waters of nearby Kusatsu. Hayao Miyazaki is documented to have visited Sekizenkan on multiple occasions, and the tunnels connecting the buildings, the red bridge over the river, and the arched halls of Genroku no Yu are regularly cited by visitors as visual sources for the bathhouse in Spirited Away.

Sansou, completed in 1936 in a Momoyama-influenced style that earned it registration as a national tangible cultural property, retains its original kumiko lattice screens and deep-toned timber. Kashoutei sits at the highest point on the property, surrounded by pines that exceed 300 years of age, and offers a different proposition: contemporary 1986 construction in an ancient landscape, with rooms ranging from standard tatami to top-floor Japanese-Western suites with private semi-open-air baths overlooking the old-growth canopy. Guests in Kashoutei gain modern comfort; guests in Sansou sleep among the structure itself. Both wings draw on the same kitchen and the same nakai staff.

The kaiseki follows a quarterly rotation in Sansou and a monthly rotation in Kashoutei, built from Agatsuma valley produce, mountain vegetables, river-caught fish, and autumn matsutake prepared in a style that preserves natural flavour rather than elaborating it. Breakfast is built around a three-hour porridge: the kitchen begins slow-cooking rice before dawn, and the dish arrives at the table with a gentleness that consistently surprises guests who expect richness after a multi-course dinner the evening before.

Service across more than 1,100 Rakuten reviews averages 4.7 out of 5, and the nakai staff here earn consistent praise for an unhurried attentiveness that does not perform formality. A guest who returned after thirty years wrote that the place felt unchanged, which captures something real about what the valley and the water hold in common. The final sensory memory most guests carry is heard rather than seen: the Shima River below, audible from the hillside rotenburo at dusk, while 900 litres per minute rise quietly through stone in the bathhouse beneath.