Obama Onsen in Unzen, Nagasaki, is famed for sunsets over Tachibana Bay and for spring water near 100°C – the highest heat output of any onsen town in Japan. Hama-no-Yu is the city-run, old-fashioned public bath of this seaside spa: a classic sentō layout with an attendant's booth and two deep tubs, hot and tepid, brimming with alkaline simple spring water. No soap or shampoo is provided (sachets are sold) – there is nothing here but the water, and bath lovers cherish that purity. Admission is an astonishing ¥150 for ages 6 and up (Unzen residents ¥100), free under 6; open 6:00–22:00 (last entry 21:30), irregular closures. Park free at the nearby Yūhi-no-Hiroba lot (10 spaces). Along the shore are Japan's longest footbath, the 105 m 'Hot Foot 105', and steam cookers, and it is fun to bath-hop to the Wakihama public bath (¥200). About an hour from Isahaya Station by Shimabara Railway and Shimatetsu bus, or an hour by car from Nagasaki city. Taste Unzen's mountain baths and Obama's sea baths in a single day.

✔ Verified operating: 2026-09 るるぶ&more（6歳以上150円 市民100円・6–22時 受付21:30・不定休・駐車10台）／雲仙観光局（無休表記・150円）

Prices and hours change. Check official sources before visiting.

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Unzen Kojigoku Onsen-kan

A historic cure-bath in the hills a short way from Unzen's main street, said to have hosted Siebold and Yoshida Shōin. An octagonal wooden bathhouse with milky sulfur water cooled from a 90°C source. No open-air bath, but Unzen's finest water.

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Unzen Yokayu

A day-bath with a simple lodging near the entrance to Unzen Jigoku. Every tub is free-flowing milky sulfur water — indoor, open-air and four private outdoor baths. ¥500, 9 am to 9 pm; an easy stop before or after touring the 'hells'.

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Obama Onsen Wakihama Public Bath (Otasshan-yu)

A communal bath in Obama Onsen on Tachibana Bay, whose ~100°C springs release more heat than any in Japan. The single-storey wooden building from 1937 feels like a museum of Showa-era life and is a designated prefectural townscape asset. Pay at the old-style counter, then choose between the hot and very hot tubs of free-flowing chloride water. Open from 6 am; part of the Kyushu 88 Onsen trail. About an hour from Nagasaki city, on the way back from Unzen.

Day-trip onsenPublic bathhouse (sento)Day use ¥400