Kanagawa Kawasaki City
Asahiyu Gensen Yuiru
Kawasaki sanctuary boasting an ultra-concentrated natural hot spring and a submersible amber cold plunge bath
- Natural Hot Spring
- Free-flow from source
- Aufguss available
- Auto löyly available
- Aroma löyly available
- Finnish sauna
About Asahiyu Gensen Yuiru
Asahiyu Gensen Yuiru is a day-use sauna and hot spring facility in Kawasaki City, Kanagawa Prefecture. It was the first in Kawasaki Ward to attempt deep drilling to 1,200 m and struck an ultra-concentrated natural therapeutic spring whose mineral content exceeds standard levels by more than 25 times. Its signature feature is flowing the source water untreated and chlorine-free. The facility operates two sauna rooms, a high-temperature löyly sauna and a mid-temperature aufguss-dedicated sauna, with aufguss performances by trained masters held every hour. It also offers an amber-colored cold plunge bath that allows full submersion to a maximum depth of 150 cm and an ultra-strong carbonated spring exceeding 1,500 ppm, earning a reputation as one of Kawasaki's premier sauna sanctuaries.
Hot SpringONSEN
Kawasaki Asahiyu Onsen
This rare ultra-concentrated natural therapeutic spring was produced by deep drilling to 1,200 m, a first in Kawasaki Ward. The total mineral content reaches 25,800 mg, well over 25 times the typical hot spring baseline of 1,000 mg. Such a high concentration is classified as a hypertonic spring and tends to allow mineral components to penetrate the body more readily. Because the source is flowed without reheating and without chlorine, visitors can fully enjoy the freshness of the minerals and the original bathing sensation. The water is amber-colored, and its hue changes with lighting between day and night. After bathing, the body remains warm for a long time, clearly demonstrating high thermal retention.
Amber High-Carbonation Neutral-Temperature Spring
So effervescent that it is often likened to Wilkinson carbonated springs, the amber well water envelops the whole body in countless bubbles, giving the sensation of being inside a carbonated drink. The temperature sits around 30°C in the neutral-temperature zone; it initially feels cool but gradually promotes circulation, producing a unique warming sensation from the inside out. The facility also runs popular Fresh Fruit Carbonation events in which large quantities of fresh fruit are added periodically, allowing guests to enjoy seasonal aromas and varied carbonated bathing experiences.
SaunaSAUNA
löyly sauna
The defining feature is the overwhelming volume of steam produced by a sauna stove manufactured for löyly by Teknoraizukomu combined with lava stones from Mount Fuji that are rich in iron and minerals. The auto löyly at :15 and :45 each hour injects a large amount of water, about 500 ml, all at once, causing high-temperature steam to explode throughout the sauna room. The top bench becomes instantly blistering hot. A three-tier bench layout and a silence-focused design with a no-talking bathing policy create a striking contrast with the roar of steam. The high heat efficiency from stacking a large mass of sauna stones generates far more steam than typical saunas.
aufguss sauna
A sauna room specifically designed for the aufguss experience. With a high ceiling and three-tier benches that fit 5–6 people per row, it secures a spacious atmosphere that balances openness and unity. Two HARVIA tower stoves perform automatic löyly every 20 minutes, and aufguss masters lead aufguss sessions every hour. The performances combine programming, music, and aromatics into highly entertaining presentations that change each time, so every visit brings a new experience.
Cold BathCOLD BATH
Amber Submersion Cold Plunge Bath
Its greatest characteristic is the ability to fully submerge, using amber-colored well water pumped from beneath Kawasaki Ward and flowed continuously. The tub has a two-step structure separated by a handrail, with 120 cm and 150 cm depths, so users can acclimate in the shallower side before moving to the deepest section (150 cm) for full submersion. The water temperature is low, and a strong current constantly cools the skin, making the perceived temperature feel even sharper. True to its name as a submersion cold plunge bath, head submersion is officially permitted, making it a rare example in Japan. The sense of release when fully immersing the whole body after a good sweat is unparalleled. The well water also contains trace hot spring minerals, giving it a slightly viscous, soft texture on the skin.
Facility Information
- Address
- 3-1-2 Kokan-dori, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture, Japan
- Business Hours
- Monday11:00〜00:00Tuesday11:00〜00:00Wednesday11:00〜00:00Thursday11:00〜00:00Friday11:00〜00:00Saturday10:00〜00:00Sunday10:00〜00:00Holiday10:00〜00:00
Irregular Holidays
- Closed Days
- Irregular Holidays
- Gender Access
- Gender Separated
- Tattoo Policy (Communal Bath)
- No Tattoos
- Official Website
- View official site
Access
Visited by the Editor-in-Chief
The Editor-in-Chief visited in person in February 2026
The Ultimate Cold Plunge Bath Is Right Here
Read the full review
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