I’m not sure how to prepare for my new life.

There are many things to prepare for your life in Japan after receiving a job offer. But, in many cases, a large number of procedures cannot be completed until after coming to Japan. Accommodation, utilities, address registration, mobile phone contracts, opening a bank account are some examples. Whilst in your home country, research to see if there is anything that can be done online. It’s important to consult with your employer’s HR division as much as possible.