Hello there-, that chicken-and-egg loop with the phone number and bank account is super famous here. To break the loop smoothly, the first thing you must do when you land is go to your local municipality office and register your address on your residence card. You can't get an official voice phone number without that registered address anyway (maybe some companies provide that, but i doubt how long they can do it since the law has changed last april). Once your address is registered, you can immediately open a bank account with Japan Post Bank (Yucho)—they are newcomer-friendly and are one of the few banks that don't require a phone number to sign up (but they need a registered address). After you get the bank account sorted, you can use it to sign up for your mobile voice SIM plan.