Its popularity has been gaining momentum in the Kanto area. We had a trial day event in February this year, which attracted people even from Tokyo. All the sauna lovers in Hiroshima who attended the event created quite a heated atmosphere. Of course, first timers are welcome to our monthly get together (except summer time).
Also some rental tent saunas are available at any time.

Activity fee: 3,000 yen (including insurance and entrance fee to onsen)
What to bring: swimming wear, sandals, towel
Useful but not necessary: surfing poncho or gown, change of clothes
Accommodating 15 people per session (one in AM and one in PM)