Matsu-no-yu

A Shinjuku Ward bath in Kami-Ochiai that, after water testing, received a license to operate as a hot spring and has run as Shinjuku Ochiai Onsen Matsu-no-yu since 26 November 2025. It offers a rotenburo (open-air bath), a cold plunge, a hot tub, an ultrasonic jet bath, standing showers and a painted mural, and can hold luggage temporarily. It is about a 1-minute walk from Ochiai Station on the Tokyo Metro Tozai Line.