A renowned hilltop hot spring boasting 100% source flow-through baths and panoramic open-air baths
Yamanashi Kai City
A luxurious day-use hot spring facility perched on a small hill in Kai, where all baths use 100% source water in a flow-through system. High-quality sodium chloride spring water with a faint egg-like scent is poured abundantly into every tub, and you can enjoy baths of varying temperatures to suit your preference. The facility features a far-infrared gas-heated dry sauna and a smooth cold plunge bath supplied with groundwater. From the open-air baths you can take in views of Mount Fuji and the Southern Alps, and the expansive outdoor relaxation area adds to the appeal.
TypeNatural Hot Spring
A sodium chloride spring that wells up from about 1,000 meters underground. The water is slightly yellowish with a faint boiled-egg aroma, and this superb water is provided 100% flow-through from the source with no dilution or recirculation. Baths are separated into different temperature ranges, such as medium and high.
Sauna TypeDry Sauna
Stove Typefar_infrared
Capacity10people
An authentic dry sauna heated by a far-infrared gas heater. The room temperature is around 95°C, providing solid heat, and the relatively spacious interior lets you work up a good sweat while watching TV.
Water Qualitywell
Capacity6people
Located right next to the sauna, the cold plunge bath uses high-quality groundwater supplied continuously from a tap. The water temperature is around 16–18°C, not too cold, and the pleasant water feel makes for a comfortable cooldown.
Closed Days: None
2361-11 Shimomai, Kai, Yamanashi 400-0105, Japan
Gender Access
Gender Separated
Curated by an expert who visits onsen and sauna facilities every day and has explored 300+ locations — only facilities confirmed to be truly exceptional are featured.
Learn more
A renowned hilltop hot spring boasting 100% source flow-through baths and panoramic open-air baths
Yamanashi Kai City
A luxurious day-use hot spring facility perched on a small hill in Kai, where all baths use 100% source water in a flow-through system. High-quality sodium chloride spring water with a faint egg-like scent is poured abundantly into every tub, and you can enjoy baths of varying temperatures to suit your preference. The facility features a far-infrared gas-heated dry sauna and a smooth cold plunge bath supplied with groundwater. From the open-air baths you can take in views of Mount Fuji and the Southern Alps, and the expansive outdoor relaxation area adds to the appeal.
TypeNatural Hot Spring
A sodium chloride spring that wells up from about 1,000 meters underground. The water is slightly yellowish with a faint boiled-egg aroma, and this superb water is provided 100% flow-through from the source with no dilution or recirculation. Baths are separated into different temperature ranges, such as medium and high.
Sauna TypeDry Sauna
Stove Typefar_infrared
Capacity10people
An authentic dry sauna heated by a far-infrared gas heater. The room temperature is around 95°C, providing solid heat, and the relatively spacious interior lets you work up a good sweat while watching TV.
Water Qualitywell
Capacity6people
Located right next to the sauna, the cold plunge bath uses high-quality groundwater supplied continuously from a tap. The water temperature is around 16–18°C, not too cold, and the pleasant water feel makes for a comfortable cooldown.
Closed Days: None
2361-11 Shimomai, Kai, Yamanashi 400-0105, Japan
Gender Access
Gender Separated
Curated by an expert who visits onsen and sauna facilities every day and has explored 300+ locations — only facilities confirmed to be truly exceptional are featured.
Learn more