At this point you've been in Tokyo for a couple hours. Maybe you've found your hotel, someplace to eat, or maybe you've taken in that drink that you've earned for all your hard work.
But your fun will be short-lived unless you get some cash.
Here's the thing: Japan works on cash, not credit cards. Unless your only expenses come from five-star hotels, most places you come across won't take plastic. You will need to get some cash to keep the wheels greased on your trip.
You get cash from postal ATMs. The Japanese postal system also runs a huge bank, and you'll be using their ATMs. ATMs also give the best exchange rates. It's safe, and normal, to carry large amounts of cash in Japan. So normally you'll get cash at the post office. There's also a postal ATM at Narita Airport, and it's near the currency exchange counter. It's marked with the Japanese Postal Bank logo, which is the green thing on the right.
Post offices on the street are marked by the signs in the picture you see here. The circled red-on-white symbol is the old-school post office symbol, and the orange sign beneath it is the new logo. Every neighborhood in Tokyo has a post office, so you're never very far away from one.
When I visit I take out around 50,000 yen ($500) to make sure the cash lasts several days. It's safe and normal to carry around that much money.
You'll take out cash directly in yen, and the equivalent in your own currency will be what's withdrawn from your account, plus a small fee (like $5, or 3%) for changing the currency automatically.
Warning! ATMs are only accessible during business hours and only on weekdays. ATMs close - yes, close - at 5:00PM on weekdays and may not be not open on Sundays. Japan is weird that way. Plan your cash withdrawals in advance.
Taking money out in large chunks may be uncomfortable at first, but it's perfectly safe, convenient, and reduces the transaction fees that might hit your credit card.
Now that you've got some cash, why not celebrate with some tasty food?