Formal — to staff
Onsen · Sento
You
すみません、この小さなタオルは浴槽に持って入っても大丈夫ですか？
すみません、このちいさなタオルはよくそうにもってはいってもだいじょうぶですか？
Excuse me, is it okay to bring this small towel into the bathtub?
Romaji: Sumimasen, kono chiisana taoru wa yokusō ni motte haitte mo daijōbu desu ka? / Reply Romaji: Hai, naka ni motte hairu no wa daijōbu desu. Tada, yokusō ni irezu, atama ni noseru ka karada o fuku no ni tsukatte kudasai.
Reply
はい、中に持って入るのは大丈夫です。ただ、浴槽には入れず、頭に乗せるか体を拭くのに使ってください。
はい、なかに持ってもはいいるのはだいじょうぶです。ただ、よくそうにはいれず、あたまにのせるかからだをふくのに使ってください。
Yes, it's okay to bring it in. However, please don't put it in the bathtub; use it on your head or for wiping your body.
Gesture & etiquette
Hold up the small towel and point towards the bath area with a questioning look.
Never put your towel or anything else into the onsen/sento bathwater, as it is considered unsanitary. Do not wash your body in the bath itself, only outside of it.