How can change country of App Store

I moved to Japan from UK, and my iPhone still connects to UK App Store.

It seems updating my address and phone number to the Japanese one doesn't much help.

(And now I don't see how to change the payment detail in Apple ID section at Apple UK??)

How can I change the registered country?

Also credit card that I use to?

Please help me out of this mystery! Thank you Appleties!