Formal — to staff
Public · Bath · Onsen
You
すみません、このタオルはお風呂に入れない方がいいですか？
すみません、このたおるはおふろにいれないほうがいいですか？
Excuse me, is it better not to put this towel in the bathwater?
Romaji: Sumimasen, kono taoru wa ofuro ni ire nai hou ga ii desu ka? / Reply Romaji: Hai, yubune ni wa irenaide kudasai. Atama ni oku ka, yubune no soto ni oite kudasai.
Reply
はい、湯船には入れないでください。頭に置くか、湯船の外に置いてください。
はい、ゆぶねにはいれないでください。あたまにおくか、ゆぶねのそとにおいてください。
Yes, please don't put it in the tub. Please place it on your head or outside the tub.
Gesture & etiquette
Point to the small towel and then gesture towards the bathwater with a questioning look.
Do not put the small towel (kakeyu towel) into the communal bathwater. It's generally used for washing or wringing out before entering the bath, then placed on your head or beside the bath.