Rich in active gases or metals — a strong mineral character.
Buoyancy
Standard buoyancy
LowHigh
Soft water — natural, classic buoyancy.
SoufreSulfuresSulfates
Fukiage Rotenyu, in Kami-Furano, Hokkaido, is notable for sulfurous water emerging at a high temperature, around 62°C. The site includes an indoor bath, an open-air rotenburo and a sauna.
Insider tip — Fukiage Rotenyu (吹上露天の湯) is legendary among Japanese onsen enthusiasts — a completely free, gender-mixed (konyoku) outdoor wild bath in the lavender country of Kami-Furano. The spring bubbles up from the volcanic ground at high temperature; there are no facilities whatsoever. Visit at dawn for the most solitary experience — it can get crowded midday in summer.