Kamata’s Four Black-Water Baths: Which One Fits Your Visit?
Compare Kamata Onsen, Hasunuma, Kaiseiyu and Yu City by natural black spring water, hot or cold pools, sauna and station access.
In Ota City, “black water” is not a single bathhouse’s branding. Several neighbourhood sento draw on the area’s dark natural spring water, and each has found a different way to use it. All four baths below charge ¥600 for adult entry under Tokyo’s current public-bath rate. The decision is about the extra baths, the sauna and how much time you want to spend there.
| If your priority is… | Best fit | What stands out |
|---|---|---|
| Very hot water and an old-school sento | Kamata Onsen | Separate hotter and cooler black-water baths, sauna and a second-floor dining hall |
| Sauna plus a source-fed cold bath | Hasunuma Onsen | Its baths use natural spring water; the cold bath is explicitly described as source-fed |
| A black-water bath with carbonation | Kaiseiyu | Black spring water, carbonated bath, cold bath and a fish tank beside the bathing area |
| A short walk from JR Kamata and somewhere to sit after | Yu City Kamata | Sauna, semi-open-air bath and YCK Hall upstairs |
What the extra ¥300 gets you
Adult entry is ¥600 at all four bathhouses; children’s rates follow Tokyo’s public-bath tariff. Sauna add-ons and towel packages differ:
- Kamata Onsen charges ¥300 for its sauna. Its ¥900 bare-essentials package already includes adult entry.
- Hasunuma Onsen charges ¥300 for the sauna, including bath and face towels.
- Kaiseiyu does not currently list a sauna; its distinction is the range of black-water pools.
- Yu City Kamata sells a combined bath-and-sauna ticket for ¥900.
| Bathhouse | Adult entry | Sauna | Best reason to choose it |
|---|---|---|---|
| Kamata Onsen | ¥600 | +¥300 | High-temperature black water and dining |
| Hasunuma Onsen | ¥600 | +¥300, towels included | Spring-fed cold bath and tattoo-friendly policy |
| Kaiseiyu | ¥600 | No sauna listed | Black-water carbonated bath and fish tank |
| Yu City Kamata | ¥600 | Bath + sauna ¥900 | Semi-open-air bath and an upstairs rest space |
The water, in four different moods
Kamata Onsen is the one for people who actively like very hot baths. It separates the black spring into hotter and cooler pools; the facility says the hotter one can approach 50°C on some days. That is not a target to endure. Start in the cooler bath and leave the hotter one alone if it feels uncomfortable. The dining hall upstairs is open on an irregular schedule, so check before planning dinner around it.
Hasunuma Onsen is a more balanced first stop. Its official site says all bathing pools use natural spring water, and specifically identifies the cold bath as source-fed. There is also a carbonated bath and a sauna. The entrance is only about two minutes from Hasunuma Station, and the facility’s FAQ explicitly allows guests with tattoos.
Kaiseiyu’s carbonated bath is the unusual one: artificial carbonation is added to the dark spring water. It also has a black-water cold pool and an aquarium beside the bath. Think of it as a compact soak with a clear visual identity, not a sauna destination.
Yu City Kamata balances the bathing part with somewhere to unwind afterwards. Its semi-open-air black-water bath and sauna sit above a station-side sento; YCK Hall provides a place to sit, eat or have a drink. It is the most convenient if you want to finish near JR Kamata rather than walk back from Nishi-Kamata.
A simple way to choose
For your first Ota black-water bath, Hasunuma is the least complicated introduction: short station walk, several natural-water pools and a clear description of the cold bath. If you want an unmistakably different second visit, try Kaiseiyu for its carbonated black spring. Choose Kamata Onsen for the hotter bathing style and its Showa-era dining-hall atmosphere. Yu City is the practical pick when location and post-bath seating count as much as the water.
Two-bath evenings are possible, but not necessary. Hasunuma and Kaiseiyu make the clearest comparison because one has a source-fed cold bath and sauna while the other centres on the carbonated black-water pool. If the sauna matters most, skip Kaiseiyu and compare Hasunuma with Yu City instead.
Read the individual Kamata Onsen guide, Hasunuma Onsen guide and Kaiseiyu guide before setting out. Their hours and occasional maintenance closures can change.
Sources
- [Kamata Onsen: current hours, fares and facilities](https://kamata-onsen.com/about/) - [Hasunuma Onsen: prices](https://www.hasunuma-onsen.com/price/) - [Hasunuma Onsen: source water, access and tattoo FAQ](https://www.hasunuma-onsen.com/faq/) - [Ota City Tourism Association: Kaiseiyu and recent local feature](https://www.o-2.jp/feature/nishikamata-sento-malatang/) - [Yu City Kamata: official site](https://youcity26.com/) - [Ota City: hot springs and public baths](https://unique-ota.city.ota.tokyo.jp/charm/health/pickup-202112-2/) - [Tokyo Metropolitan Government: public-bath admission rate effective 1 August 2026](https://www.metro.tokyo.lg.jp/information/press/2026/07/2026072121) Checked: 2026-09-27Tags: Kamata black water, Ota City onsen, Kamata Onsen, Hasunuma Onsen, Kaiseiyu, Yu City Kamata
