store region availability update

Hi,

I have an iOS app available in every regions in the world on the app store. I want to update the app and make it available in Japan only because of some right management questions.

I want to know whether people that have already downloaded the app and have already made an in-app purchases from another country (for ex: USA ) will still be able to buy content inside the app after I changed its availabitily to Japan only.

Thank you for your help.