Izu Hatake Onsen Seizan

Seizan is a therapeutic bathing inn (toji-yado) in Hatake, Kannami Town, Shizuoka Prefecture, set in the quiet farmland at the southwestern foot of the Hakone caldera rim. Hatake Onsen has served as a healing retreat since the early Edo period, with bathing records reaching back more than 400 years. Local tradition holds that Minamoto no Yoritomo rested his warhorses here, and the poet Wakayama Bokusui wrote of these waters. In 1962 it was designated a National Health Resort Spa, together with neighbouring Nagoya Onsen. Seizan traces its lineage to Kinkeisha, founded in 1888, which later became Takahashi-kan and then the separate Takahashi Bekkan in 1964; the building was thoroughly renovated and reopened under its present name in 2018.

The spring is an alkaline simple hot spring with a pH of 8.7 and a source temperature of about 30 degrees Celsius. The water is colourless, clear, odourless and notably soft, long known locally as the lukewarm sacred spring. The indoor bathhouse holds three tubs, all fed by the same source: one at the natural 30 degrees, one near body temperature at 35 degrees, and one warmed to around 42 degrees. The 30-degree tub runs as pure free-flowing spring water with no heating and no added water, and alternating between the cool and warmed tubs is the signature way to bathe here. The waters are recommended for high blood pressure, neuralgia, rheumatism, digestive complaints and joint conditions, and are prized for their effect on the skin.

Bathing facilities comprise the main indoor bath with its three tubs, an open-air bath enclosed by bamboo groves, and a private room bath available by reservation for 3,000 yen per hour. Day visitors are welcome from 9:00 with last admission at 20:00; two hours costs 700 yen on weekdays including the 150 yen bathing tax, three hours 870 yen, and a full day 1,000 yen. The in-house cafe restaurant Kuon, known for its gyoza, gives bathers a 100 yen discount. Overnight stays start at 11,000 yen with two meals, and multi-night therapeutic plans such as four days and three nights for 30,000 yen are also offered.