Kaiseiyu

This was my first time visiting. There are four bathtubs: a silk bath, a black water bath, a massage bath, and a carbonated spring bath, and each is not very large. The water temperature is not too hot and is comfortable. All of the washing areas are equipped with showers, but they are push-button type, which can be a bit of a hassle. There is also an area for hair dyeing, which is unusual, but it seems they are being discontinued due to poor manners. There are no painted pictures, as is common in bathtubs, but instead there is an aquarium with goldfish swimming in it, which is unusual. There is no shampoo or body soap. Hair dryers cost 10 yen for 2 minutes. Without a sauna, it is a public bath where you can relax and enjoy time.

2025/11/26 I visited Nojiru Sento @Kaisei-yu. I liked the black water carbonated spring and the silk water with its extremely fine bubbles, but... The shower only comes out when you press the faucet, so it was a struggle to wash my hair. I went to the (old) hair dye booth to wash my hair. I wish it would stay out for at least 5-10 seconds even after you let go. I bought a "black water dyed coffee milk towel." I don't want to visit again if the shower stays like that, so I'm moving on to other black water sento.

This was my first time at an onsen and everything was straight forwards, I paid my entry and then didn’t realise I needed a coin for the locker (I ended up leaving it unlocked and closed the door, all my things were left untouched). They had signs with pictures to tell you what to do etc.. but my favourite part was how casual everyone was there as they all kept to themselves and I had so much fun relaxing and watching the fish. Definitely will go back again, also the black water left my skin so smooth.

The black water sento was soooo amazing!! There were three different temperature options for the black water pools. Then there was a silky bath and a regular water bath that even had a personal jet area. Make sure you bring your own towel and soap! Everyone was so nice and helpful here 😊 …

It's an awesome public bath in Kamata area. Especially, their chilled water tub is refreshing and one of many reasons I go to Kaisei-yu rather than others. Pretty great!