A 400-year-old hot spring inn standing alone deep in the Ogawa river gorge that runs down from the Northern Alps in Asahi, the easternmost town of Toyama. Known as a fertility and therapeutic spa, it offers a circuit of five different baths. The great curiosity is the 'natural cave open-air bath', a dome of travertine built up over centuries from the spring's own mineral deposits and designated a prefectural natural monument – bathing inside it is an experience found nowhere else in Japan. There are also the streamside Renge-no-Yu outdoor bath, a rock bath and a cypress tub, all with free-flowing bicarbonate spring water that keeps you glowing long after. Day bathing runs 9:00–15:00 (reception until 14:30) for ¥1,000 per adult and ¥500 per child, or half price for the outdoor baths only. Irregular closures, and the two outdoor baths shut for winter from 1 December until the mid-April thaw. About 15 minutes by car from Tomari Station on the Ainokaze Toyama Railway, 30 minutes from Kurobe-Unazuki-Onsen Station on the Hokuriku Shinkansen (shuttle for overnight guests) or 15 minutes from Asahi IC. A hidden spring to pair with the Jade Coast and Unazuki on a drive along the Niigata border.

✔ Verified operating: 2026-09 朝日町観光協会公式（日帰り大人1,000円 小学生500円・9–15時 受付14:30・不定休・野天風呂12/1–4月中旬閉鎖）／とやま観光ナビ

Prices and hours change. Check official sources before visiting.

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