What would it feel like to bathe in that black water from a Magic 8 Ball? Well, you can do that at Tenjin-yu in Shinagawa-ku. I stopped off here on the way to Haneda airport and was glad I did. This is a very おしゃれ (fancy) sento on the first and second floors of a larger apartment building. The baths are on the second floor. Enjoy the wall art as you make your way up the stairs.

This is a smaller sento with one main bath separated into normal and extra hot (45°C) sections. The inside water is municipally sourced and has a very apparent amount of chlorine. That said, the water felt very clear and fresh. This goes for the washing stations also.

In the quasi-outdoor area is the black water natural hot spring-filled tub. This is technically not a hot spring as the well temperature is only 17°C. However, mineral springs like this one typically turn out to be the best water for soaking, especially after it is heated up to 40°C. This water's feel, smell, and color were all mesmerizing. The water felt like ink with a slipperiness to it. The smell reminded me of a car parts store with all the rubber tires. The color reminded me of changing the oil in my car. Notably, it didn't seem to stain my white towel.

No saunas here or cold baths. Thankfully two showers near the entrance get cold enough to adequately cool off.

Highly recommend.