For those of you who’d like to enjoy a hot spring bath with a significant other, or a group of friends, without having to be naked, here is a list of facilities where bathing suits are required in areas shared by males and females.
Enoshima Island Spa outdoor baths

1) KANAGAWA PREFECTURE – Enoshima Island Spa: a self-contained spa complex on the island of Enoshima, beside Kamakura. The facility has segregated (naked) hot spring baths indoors, and other areas containing pools where bathing suits are required. Some of them are outdoors, just above the ocean, with Mt. Fuji views. Access: Take train to Enoshima Station or Shonan Enoshima Station and walk out to the island. Or, take a bus from Fujisawa Station.  http://enoshimaislandspa.com

2) KANAGAWA PREFECTURE – Hakone Yunessun: An onsen ‘theme park’ with waterslides, and a variety of interesting indoor and outdoor pools. The sake, green tea, and red wine baths are especially popular. Access: Take a bus from Hakone Yumoto Station. http://www.yunessun.com/english/  

3) SAITAMA PREFECTURE – Shinrin Koen Heritage Resort: Their onsen facility, Toki-no-yu, has separate (naked) onsen baths and mixed outdoor pools at the base of a waterfall where bathing suits are required. Access: Free shuttle bus from Shinrin Koen and Kumagaya Stations.  http://www.hotel-heritage.co.jp/en/

4) SHIZUOKA PREFECTURE – Atami Marine Spa: A family-oriented facility containing a mini waterslide, short ‘lazy river’, swimming pool, sauna, Jacuzzi area, and rooftop open-air shallow pool. There are also segregated (naked) onsen baths on a separate floor. Access: Take bus or taxi from Atami Station.  http://marinespa.com

5) CHIBA PREFECTURE – Oedo Onsen Monogatari Urayasu Mangekyo: Another onsen ‘theme park’ with 38 different types of hot springs including one that guests can enjoy while wearing a bathing suit. Access: Free pick-up service available from Shin-Urayasu Station.  http:/urayasu.ooedoonsen.jp

6) TOCHIGI PREFECTURE – Kinugawa Nioson Plaza: There are three open-air baths here, including a boat-shaped one overlooking the Kinugawa River called ‘Butai-no-Yu’ in which swimsuits are allowed.  http://www.niousonplaza.com

7) TOKYO – Toshimaen Niwa-no-yu:  The facility is located only 3 minutes on foot from Toshimaen Station on the Oedo Subway Line and Seiyu Ikebukuro Line in Nerima Ward.  It has separate male & female areas, with a co-ed bathing suit section in between.  http://www.niwanoyu.jp/niwa/