If you buy a suitable unlocked refurbed phone , check here
https://www.frequencycheck.com/country-compatibility/MnNRM/japan/devices
it will come without SIM or contract.
MOBAL will provide the SIM card and short term contract and tel No, delivered to you before departure (if time) or pick up in Japan, only activated when you need it.
For your stated requirements you would pick the 30 day Voice+Data SIM on the earlier web site I mentioned and click on more details, read it all, all the info is there and in the FAQ's