Kanto Hakone, Kanagawa
Hakone Kowakien Yunessun Mori no Yu
箱根小涌園ユネッサン 森の湯
Name in Japanese. Look for this on the sign, or show it to a taxi driver.
Allowed with conditionsStated by the facility
Super sento (large day-bath complex). Water source not checked; see the official page
Tattoo rule
Allowed with conditionsStated by the facility
What the official page says
日帰り温泉「森の湯」は、当館指定のタトゥーカバーシール（有料）2枚で完全に覆える場合に限り、ご利用いただけます。
In short: Tattoos must be fully covered with cover stickers (up to 2 stickers), using the facility's paid cover stickers.
Where it is
Kanto region, Kanagawa prefecture. About 6 km in a straight line from Hakone.
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Rules can change. Check the official page on the day you go. Any paid link is labelled next to the button. We have not visited this bath ourselves.