Irori no Yado Shichirigawa Onsen

Tucked deep in the Boso Hills at the headwaters of the Obitsu River in Kimitsu City, Chiba Prefecture, this solitary inn traces its hot spring back to June 1984, when the source was first opened. Innkeeper Mamoru Suzuki began operating the lodge in July 1995; what started as a pension-style building became known for an irori (sunken hearth) installed in a meeting room, which proved so popular that the inn eventually built a custom, oversized hearth.

The spring is a simple sulfur spring (tanjun-io-sen), a rarity in Chiba, with a pH of 7.9. Because the source emerges at a cool 15°C, the water is heated before reaching the baths, but the official website states that the hot spring water is entirely gensen kake-nagashi (drawn straight from the source), continuously replenished rather than recirculated. The faintly yellow-tinged water has a smooth, silky texture and is said to help with rheumatism, neuralgia, injuries, and gynecological conditions.

The bathhouse offers two indoor baths and three open-air baths, alternated between men and women. The highlight is grilling seafood, dried fish, and wild boar over the communal hearth. Day-trip bathing costs 1,150 yen for adults and 500 yen for children, available from 8:00 a.m. to 10:00 p.m. (last entry 9:00 p.m.); overnight stays are in one of five Japanese-style rooms, starting at 13,900 yen per person with two meals.