Kamata Onsen

Located in the Kamata-Honcho neighborhood of Ota Ward, Tokyo, this hot-spring bathhouse (sento) opened in 1937. It is said that patients from a nearby hospital once used it for therapeutic bathing in the postwar years, and it remains a beloved neighborhood institution. The current building was rebuilt in 1986 and sits within walking distance of both JR Kamata and Keikyu-Kamata stations.

The water is a sodium bicarbonate-chloride spring. Its humic-acid-rich black water (kuroyu) is regarded as among the darkest in Ota Ward — dip your hand in and it vanishes just centimeters below the surface. Since the source is a cool mineral spring at roughly 18°C, it is heated before use and filtered through a circulation system with chlorine disinfection for hygiene.

The bathing area includes hot and cool black-water pools, an electric bath, a jet bath, a cold plunge, and separate saunas for men and women, with a cafeteria and banquet hall on the second floor. Open year-round from 10:00 a.m. to midnight. Admission is 550 yen for adults, 200 yen for children aged 6-11, and 100 yen for children under 6.