Hoshi Onsen Chojukan

A lone Meiji-era inn where the water bubbles up through the stones beneath you — one of Japan's great baths, if you can handle mixed bathing, no air conditioning and autumn stink bugs

Chojukan is the only inn at Hoshi Onsen, at the end of a mountain road in northern Gunma, and its reputation rests on one room: Hoshi-no-yu, an 1895 wooden bathhall where the hot spring rises straight up through the pebbles under you, never touching the air. Japanese guests score the baths higher than anything else — 4.8 on Jalan (1,112 reviews), 4.72 on 一休 and 4.71 on Rakuten, against overall scores of 4.3, 4.25 and 4.39 (521 reviews) — and the 1875 main building, the bathhall and the 1940 annex are all registered cultural properties. Guests love the hearth kept burning all year, the sound of the river and being able to use the bath all night: as one put it, that is 'the privilege of staying'. Hoshi-no-yu remains the top draw, though Tamaki-no-yu, the cypress bath, is increasingly named a favourite. Two things put people off. Hoshi-no-yu is mixed-gender except for women-only time from 20:00 to 22:00, and no swimwear or towels are allowed; several women found it daunting, and recent reviews say women's time is short and crowded, with men lingering, staring and even walking in during women's hours. The inn now holds occasional women-only stay days (September 2026; next 16–17 December 2026), when all three baths are open to women at any time. And these are old buildings: most rooms have only a fan — Room 15, renovated with air conditioning and beds, is the exception — walls are thin, there are stairs and no lift, and autumn reviews count stink bugs by the dozen. Food is hearty mountain cooking — carp, ayu, deer, Joshu beef sukiyaki — and scores lowest, with complaints about dishes arriving all at once or going missing; several 2025–2026 reviews also mention communication gaps with staff, though others praise them.