Multiple residences and Juminhyo

I have a house in Niigata (purchased) which was my main residence and I also have a rental apartment in Okinawa prefecture and planning a buy a house in Okinawa. I have my juminhyo registered in Niigata prefecture with Niigata address.

I'm planning to live more permanently in Okinawa and come to visit Niigata for a few months every year.

Do I need to cancel my Niigata juminhyo and apply for a new one in Okinawa? Or can I have my address updated to Okinawa address on my Niigata juminhyo? If the latter, do I do this in Niigata or in Okinawa?

I tried to buy a car in Okinawa and I was told that I need an Okinawa juminhyo. If I only update my address on the juminhyo to Okinawa but remains a Niigata juminhyo, will I be able to buy a car?

Thank you

What you need to do is go to your city office in Niigata and complete the move-out procedure, then go to the one in Okinawa and complete the move-in one. Then you will be registered as resident in Okinawa (and not in Niigata any more) and you can obtain a juminhyo copy in Okinawa.