Kaikake Onsen is a secluded one-inn hot spring ryokan located at approximately 700 meters elevation within Joshinetsu Kogen National Park in Yuzawa Town, Minamiuonuma District, Niigata Prefecture. As a member inn of the Japan Secret Hot Springs Association, it has been known as a 'hot spring for eyes' since the Edo period and is one of Japan's three major 'eye hot springs.' With a history of about 700 years, it's also called 'eye medicine hot spring.'

The hot spring is a sodium/calcium-chloride spring with a source temperature of approximately 37°C and weakly alkaline properties. It's 100% source water flow-through, containing well-balanced amounts of boric acid and salt, particularly effective for eye diseases. During the Edo period, it was listed in hot spring rankings as a 'hot spring for eyes,' and many people visited for therapeutic treatment of eye diseases. It's said to be effective for eye fatigue, eye diseases, and eye disease prevention, with special hot spring water prepared for eye washing. It's also beneficial for neuralgia, muscle pain, joint pain, sensitivity to cold, and fatigue recovery.

The ryokan is a single building on approximately 9,000 tsubo (about 30,000 square meters) of land, surrounded by nature-rich environment where wildlife such as monkeys and serow live. Guests can take walks along riverside trails in yukata. Located beyond the steep 'Kaikake Pass' and narrow 'Kaikake Bridge,' it offers the full atmosphere of a secret hot spring.

Accommodation rates are from 17,000 yen per person per night with two meals on weekdays, and from 19,000 yen on Saturdays, days before holidays, and high seasons (excluding consumption tax, bathing tax of 150 yen additional). Check-in is 15:00-18:00, check-out is 10:00. Last order for dinner is 20:00, and alcohol service ends at 20:00. There are no convenience stores nearby, so it's recommended to prepare necessities in advance. Day-use bathing is generally not accepted (priority for overnight guests).

Access is by route bus (Yuzawa Town Bus) from JR Joetsu Shinkansen Echigo-Yuzawa Station for about 30 minutes to 'Kaikake Onsen' bus stop (immediate arrival), or by car from Kanetsu Expressway Yuzawa IC for about 20 minutes. Free parking is available. Direct booking through the official website offers the best rates, with reservations also available through Agoda and other booking sites. It's a precious secluded one-inn hot spring where you can enjoy the famous hot spring effective for eye diseases in a quiet mountain setting.