Tennomaru
天の丸
The inn's bath page lists tattoos as allowed in the baths, with no cover asked for and no hours attached. That line sits under the list of every bath in the building: the two view open-air baths, the two large baths and the two private open-air baths. The baths are for staying guests only at present.
タトゥー・入れ墨の入浴可
Best for: bathing with tattoos uncovered in an open-air tub that looks down on Gamagori and Mikawa Bay at night
Only the open-air baths carry hot spring water: the view open-air baths Southern Cross and Swan Cross on the 4th floor and the two private open-air baths. The inn says its large baths, Mikawa-no-yu and Aoi-no-yu in the basement, are not hot spring water, and that the open-air tubs in the Geshokyu rooms are not hot spring water either. Private open-air baths: 45 minutes for 3,300 yen, by reservation, 3 to 10 p.m. Day-use bathing is suspended for now.