Hasunuma Onsen
Ōta, Tokyo, Japan
- Location
- Ōta, Tokyo, Japan
- Water type
- sodium chloride, thermal
- Temperature
- 42 °C
- pH
- 7.3
Water profile
Thermicity
Sedative
LowHigh
Relaxing — deep, immediate muscle release.
Mineralisation
Restorative
LowHigh
Loaded with major ions — the essential minerals (Ca, Mg).
Buoyancy
Effortless float
LowHigh
Dense, salty water — you float without effort.
SodiumChloruresBrome
Hasunuma Onsen is located in Ōta ward, Tokyo. The sodium-chloride, thermal water emerges at a notably warm 42°C, pH 7.3, right in the heart of the capital. An indoor bath, an outdoor rotenburo bath and a sauna are available.
Insider tip — 'Hasunuma Onsen' (蓮沼温泉 — lotus swamp spring) in Ōta-ku (Ōta Ward), Tokyo — one of the ancient marshland neighborhoods of the Tama River delta, where lotus flowers once bloomed in the tidal swamps. Tokyo's urban onsen draw from deep artesian wells (1,000-2,000 m), producing dark brown-black sodium-chloride water — ancient sea sediments compressed into highly concentrated brine over millions of years. These black 'kuro-yu' (black waters) are extraordinarily warming and skin-conditioning, a Tokyo specialty unique in the onsen world.
Nearby
Frequently asked questions
How hot is the water?
The water runs quite hot here, around 42 °C — a sedative water that brings immediate muscle release.
What type of water is found here?
This spot features sodium chloride & thermal water.
What is the best season to visit?
The most favourable period for this spot is: Toute l'année.