Getting A Cellphone

I want to know how y’all set up yourself to get a phone. Did you call your phone company to have your phone set up so you weren’t without a phone when getting to Japan or did you go a few days without and then go get a phone when you got there?

This stumps me honestly, this is the only place I feel I can get a clear cut understanding and answer. I kinda don’t wanna be without a phone but if I have to, I will.