How to change my Apple ID payment method in Japan?

To me it looks like you have been paying by mobile billing. Maybe that was backed by your credit card to your carrier? Anyway, it appears there was a problem with that and since subscriptions require a card be present you got the second message. Contact your carrier and/or your credit card company about this issue. I suspect all Apple knows is it tried to bill your carrier because you use mobile billing and that failed. They probably don't know why, just that they were told "no".

If you did indeed have a credit card as your payment and it needs updating, enter the new card first, then you can delete any old one. If you have problems doing this then contact Apple about the issue. Note, however, that if you are living in Japan you are supposed to be using Japan as your ID country. Since you do not you may find this raises issues.

Can you ell us why you cannot? Error messages?

See this article for information about updating payment methods on various platforms (iPhone, Mac, etc.): If you need to change or update your Apple ID payment method - Apple Support