Happo-no-Yu
白馬八方温泉 八方の湯
No cover and no private room needed. Happo-one Kaihatsu, the company that runs all four Hakuba Happo Onsen day baths, answers the question in the FAQ on its own inquiry page: people with tattoos may use its baths. The English version of the same page says they are welcome.
当店はタトゥーのある方もご利用いただけます。
Best for: The biggest of the Happo day baths, open every day of the year until nine at night
Open all year, 10:00–21:00, last entry 20:30, no regular closing day; it shuts for maintenance on announced dates. Adults 1,000 yen, elementary-school children 600 yen, ages 3 to preschool 400 yen. Indoor and open-air bath on each side, no sauna. Soap, shampoo and dryers free; towel 300 yen, rental towel set 600 yen. Cards and QR payment accepted. Swimsuits are not allowed. The operator’s English FAQ wording: “People with tattoos are welcome to use our facility.” A baby bath and baby chair are kept here. Mixed bathing for children stops at age 6.