This natural onsen is rather oddly located between a UNIQLO and a gym in the western half of Setagaya. Like Yumori no Sato not too far away, the appeal is the naturally black spring water which the onsen draws from 1,200 meters below ground. Due to its high alkaline nature, it has a slightly slipperiness to the touch and is said to be good for the skin. Other than the black water, the bathing area is fairly standard. One large main bathtub set at about 41°C, a few single-person tubs where you can lie down and relax as bubbles fire at you from various directions, a smaller outside bath, one pot tub, and a dry sauna. The onsen obviously has to do as best it can with its location inside a nondescript building. The outside does have some plants and benches and create a relaxing environment, but ultimately it’s not the best of Tokyo’s onsen if you’re in search of a bit of solitude.
There’s a family restaurant attached to the onsen with both western and Japanese style seating, a relaxation room with comfy chairs and individual televisions, as well as a range of other massage and beauty treatments and services.