Akashiya

Spring-source temperature

About 48°C at the source

Bathing temperature

Not published; the inn says the source cools naturally as it flows into the bath

Spring source

Iwai Onsen water

Spring classification

Calcium and sodium sulfate spring

pH

Not published

Flow rate

Not published

Water handling

The inn says its spring water is kept free-flowing. The women's hinoki bath is specifically described as using 100% spring water without added water or heating; the men's hinoki bath has spring water emerging from the floor. Those descriptions are not generalized to every bath.

The garden outdoor bath is closed from November through March. Day use can also be suspended during busy periods; it was paused August 1–18, 2026. Confirm current access before travelling. Tattoo rules are unconfirmed.