Arimakan
有馬館
Arimakan answers this in its own FAQ: guests with a tattoo of any size, anywhere on the body, may not use the large shared baths. The inn points them to its private baths instead, a seventh-floor open-air bath and three indoor baths, each booked at check-in for 40 minutes with the first session free. It also suggests the room's own bath, which the inn says is not hot spring water.
サイズや箇所を問わずお体に刺青やタトゥーのあるお客様は、大浴場のご利用をお断りさせていただきます。お部屋のお風呂をご利用いただくか、貸切風呂がございますので、そちらをご利用ください。
Best for: families or couples who want a free private hot spring bath and dinner served in the room
Four private baths: the seventh-floor view open-air bath, and on the first floor the Kihoseki standing bath (120 cm deep with micro-bubbles, and a step to sit on), Pamukkale (modeled on the Turkish terraces) and Yawaragi (flat floor, wide rim, usable by wheelchair, with a bath wheelchair on loan). The inn says the three indoor ones are source-fed. The first 40-minute session is free; later sessions cost ¥2,500 per 40 minutes if a slot is open that day. Book at check-in only; no advance booking. Hours 11 a.m. to 10 a.m. the next morning. The room baths are not hot spring water. Dinner and breakfast come to the room for up to three per room. Bath-only visits are suspended.