Kodai no Yu is a day-use hot spring facility in Katsushika City, Tokyo, about eight minutes by free shuttle bus from Shin-Koiwa Station. It has salt-tinged hot spring water, an open-air bath, and three saunas: high-temperature, medium-temperature, and steam. Towels, bath towels, and indoor clothing are lent out, and there are manga, reading areas, and a sleeping room for staying the day. Walking from Shin-Koiwa Station takes over 20 minutes, and the regular admission fee is high.