Country/Region information

Hello, I had recently changed my Country/Region information from Canada to Japan and updated all of my Apple ID as so for personnal reasons. When I go to the Apple Store to try and change it back, it doesn't let me anymore, yet I don't know why. My balance is empty so that's not the issue. I will provide you with a screenshot of what I see when I do try to change it.

Please do tell me the reason behind this and why it's not letting me change the Country anymore.

Thank you.