受付で確認したら、「タオルで少し隠す感じの配慮をお願いします。もし他のお客さんからクレームがきたらアウトです」と笑いながら言われました。

I put it in without any problem

It is all right as long as it is not entirely on the back. (Fashionable tattoes are basic OK) We are not accepting anything at the reception desk, but if you can use it I was told that it would be nice if you could do something to hide a little with a towel.