You're talking about cash, right? Not the total budget for two weeks.

1. Do you intend to use a credit card for most transactions?
You can use cards for most things. Over two weeks, if you take care to avoid shops that don't take cards, you might even get by without using cash. That said, you should probably have at least 10,000 JPY on you in case you find yourself in one of the very few remaining taxis that doesn't take cards, or you have dinner somewhere and realize at the last moment that the restaurant doesn't accept credit cards.

2. Do you have at least one ATM card with a pin number that you can use to withdraw cash from an ATM? Check that you can use it at 7 Bank ATMs.
https://www.sevenbank.co.jp/intlcard/card2.html

I suggest that you withdraw 10,000 to 30,000 JPY from an ATM when you arrive in Japan and only make further withdrawals when your cash reserve gets low. You should quickly get a sense for how much cash you'll need for the whole trip.