Opening a bank account in Japan is essential so that you can sign up for cell phone service, receive direct deposits from work, among many other useful things.
Japan is a largely cash-based society. When you come to Japan, we recommend that you bring a minimum of about ¥40,000 to cover transportation and living costs.
While Japan is mostly cash-based, large payments for things like rent are often handled at an ATM through a bank transfer. They can be made using cash at many ATMs.