How old do kids stop bathing with parents?

My grandpa is going to take me and my sister to Japan next summer. I know it's common for families to bathe together, but how old is this done until? I am 9 and my sister is 13. Can we bathe by ourselves?

There is no written rule and it differs from family to family. What's more important is; do you feel comfortable taking a bath with your grandpa? Many Japanese kids insist on taking a bath on their own by age 9, but even not you have the right to decide yes or no.

Jenny,

As suggested, it's very unusual for a parent in Japan to let 9 year olds or older people to bath with someone of the opposite genger even if it's her own grandfather. But it's up to you.

Meanwhile, if you go to big onsen baths etc., you might be encouraged to bath with strangers of your own gender in a huge bathing room. Again, it's up to you to refuse or not.