Canada was kinder to me: a prepaid phone plan needed nothing, and the bank accepted it straight away.
Japan edition of the chicken-and-egg problem! When I arrived I needed a residence card (got it at the airport, yay), then an address registration at the ward office, then a bank account, which wanted a phone number, and the phone contract wanted a bank account. For about ten days I had neither.
In the end a colleague took me to a phone shop that accepted a credit card from home, and then the bank accepted my new number. But I've heard so many versions of this loop from people in other countries. How did you break yours?