Can a tourist get insured on a local car owned by a Japanese Citizen?

My family in law own a car in Japan.

We visit them several times a year for over a week. I would like to be able to drive their car, rather than rent a car every time.

I have a international driving license, I don't have a Japanese driving license.

Is it possible to be added to their car insurance, or can I buy insurance separately on my own?

Thank you