Change Apple ID from "only valid for purchases in" another country

I've an iPhone 7 Plus. I already created my Apple ID in Sri Lanka. Now I live in Japan. I want to set my App Store country/region to Japan. How do I do it?

You can change your App Store country with the Support document by Apple which is given below. Please note that all your current subscriptions will be cancelled.

1. On your device, tap Settings > [your name] > iTunes & App Store.
2. Tap your Apple ID. If you're not signed in, sign in with the Apple ID and password that you use with the iTunes Store.
3. Tap View Apple ID. You might be asked to authenticate your Apple ID.
4. Tap Country/Region.
5. Tap your new country or region, then tap Next.
6. Review the Terms and Conditions and Apple Privacy Policy, then tap Agree if you agree.
7. In the prompt that appears, tap Agree.
8. Select a payment method and enter your payment information.
9. Enter your billing address and tap Next.

Change your Apple ID country or region