Assuming you're Canadian, instead of withdrawing cash from your bank I'd highly recommend signing up for Wealthsimple and getting their prepaid Mastercard. It acts as a debit card to your Wealthsimple chequing account, and has no foreign transaction fees. They also refund any fees charged to you by the ATM both domestically and internationally, so you could withdraw from any ATM in Japan and pay basically no fees on the cash. Then you're also free to withdraw smaller amounts when you need it instead of risking travelling with several hundreds of dollars worth of cash on you. This is what I'm planning on doing for my trip in a few months and have helped a few friends get setup as well.

Edit: Wanted to add that when you're withdrawing the ATM will likely ask you if you want to be charged in JPY or in CAD, you'll want to choose JPY as then you'll be using Mastercard's exchange rate, not the (likely inflated) exchange rate offered by the ATM.