Shiriyaki Onsen

Published: Aug 11, 2026

Updated: Aug 11, 2026

Shiriyaki Onsenriver bathfree onsenmixed bathingNakanojo

Representative image — not a photograph of this location.

At Shiriyaki the hot spring does not come out of a pipe into a tub — it comes up through the bed of the Nagasasa River, and the bath is the river. A low weir holds back a pool roughly thirty metres across, hot water rises through the gravel underfoot, and cold mountain water runs in from upstream, so the temperature varies depending on where you stand. Find your spot, and that is the bath.

There is no building, no attendant, no fee and no closing time. There is also no changing room, which is why most people arrive already wearing a swimsuit; the pool is mixed and swimsuits are the norm in it, though the small covered bath beside it follows ordinary onsen rules and swimsuits are not allowed there. Because it is a real river, it is at the mercy of the weather: after heavy rain the flow rises and the water cools, and there are days when it simply is not usable. The trade is that on a clear autumn afternoon you are sitting in a hot river under the trees with nothing built around you at all.

Essential Information

Opening Hours

Open 24 hrs (no lighting after dark — daylight visits recommended)

Closed: Open year-round | Unusable after heavy rain or during high water

Entrance Fee

Free

Best Season

Late September–November for autumn colour over the pool | Usable year-round in fair weather

Visit Duration

45–90 minutes

Getting There

Access Information

Iriyama, Nakanojo, about 800 metres beyond Hanashiki Onsen at the end of Prefectural Route 55. Car strongly recommended. Free parking roughly 200 metres before the pool, then a short walk down. Free to use, no fixed hours. No changing rooms — arrive wearing a swimsuit. Chloride spring. Flow and temperature vary with rainfall; the bath can be unusable after heavy rain.

Insider Guide

Premium

**Arrive changed.** There is no changing room and no lockers. Wear your swimsuit under your clothes, bring a towel, and bring a bag you are willing to leave on the bank. Water shoes are worth having — the bed is loose gravel and there are hot patches directly over the seeps. **The temperature is a map, not a number.** Water enters hot from below and cold from upstream, so the pool has warm corners and cool ones. Move around until you find a spot that suits you rather than judging the whole bath from where you first stepped in. **Two different sets of rules.** The open river pool is mixed and swimsuits are standard. The small covered bath alongside is a conventional onsen and swimsuits are not permitted in it — do not carry the swimsuit habit from one to the other. **Check the weather before committing.** This is an unroofed natural river. Snowmelt and heavy rain raise the level and drop the temperature, and in those conditions the pool is cold and fast rather than pleasant. Local accommodation will tell you the current state if you ask. **Daylight is the practical limit.** Nothing closes, but there is no lighting, the approach path is unlit, and the road in is a mountain road. Treat sunset as the end of the visit unless you are staying nearby.

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