Hotel Matsubakawa Onsen

Hotel Matsubakawa Onsen is a single isolated inn set in the Hinoji River gorge in Shimanto Town, Takaoka District, Kochi Prefecture, within the headwater region of the Shimanto River. Standing at roughly 200 meters above sea level and about 30 minutes by car from the Shimantocho-Chuo Interchange, it has no neighboring lodgings. The exact date the spring was opened is unknown, but records indicate it was already regarded as a sacred healing spring during the Edo period. Today it is counted among the hot springs of the Oku-Shimanto onsen district.

Its defining feature is a pair of separate sources, a rarity anywhere in Japan. The indoor bath, named Shimanto no Yu, draws a simple sulfur cold mineral spring classified as alkaline and hypotonic, emerging at 10.6 degrees Celsius with a pH of 9.6. The open-air bath uses a different water that qualifies as a hot spring under Article 2 of the Hot Spring Act through its fluoride, metaboric acid, and sodium bicarbonate content, emerging at 17.8 degrees Celsius with a pH of 9.3. Both rank among the most alkaline waters in Kochi Prefecture, and the faint sulfur scent and silky, slippery feel have earned the spring a reputation as a bijin no yu, or beautifying bath. Because both sources emerge below 25 degrees Celsius, the water is heated before it reaches the tubs.

The bathing area includes a large indoor bath, an open-air bath overlooking the mountain stream, a cascading pour bath, a bubble bath, a sauna, and a cold plunge, plus a private bath available for an additional fee. Day-trip bathing runs from 10:30 to 21:00 with last admission at 20:30, priced at 700 yen for adults, 350 yen for children, and free for preschoolers. On Wednesdays bathing begins at 16:00 due to maintenance, and day-trip bathing is closed on the third Thursday of each month, or the fourth Thursday in August. The inn has 19 guest rooms, with rates from 7,700 yen per person including two meals featuring produce from the mountains, rivers, and coast of the Shimanto region.