According to their website, they have an announcement from March 2020 that says in both Japanese & English:
This is a request for all visitors with the Tatoos to a body
1) The large communal bath is not over the use
2) When use a beach and pool, please prevent the exposure of the Tattoo with clothes by all means.
Please wear the clothes such as T-shirts by all means.
Thank you very much for your cooperation.
https://www.moonbeach.co.jp/2020/03/15/%e3%82%bf%e3%83%88%e3%82%a5%e3%83%bc%e3%80%81%e5%88%ba%e9%9d%92%e3%81%ae%e9%9c%b2%e5%87%ba%e3%81%ab%e9%96%a2%e3%81%99%e3%82%8b%e3%81%8a%e9%a1%98%e3%81%84/