Free Wi-Fi is available at (almost) all Starbucks Coffee restaurants. Starbucks restaurants are very common in Japan’s cities and are easy to spot from a distance with their large signs and green logo.
The actual drink menu is virtually identical to that of Starbucks in most other countries and the prices are about the same.
You can connect to Wi-Fi at the restaurant. A few years ago, you had to pre-register on the internet but now it’s a quick process at the restaurant. Most restaurants have a pamphlet in Japanese and English which explains what you have to do.
You can also see the instructions if you search Google for “wi2 at starbucks japan”.
And don’t forget you can also get free Wi-Fi at here and here.
Japan Tourist Tips 