Buying a SIM without a contract is not common in Japan.

There were prepaid cell phones before but they were used criminal activities and the goverment baned.

Now some companes started to sell a prepaid SIM in Japan.

But they are not for foreign tourists and only has Japanease instrustions.

Anyway, you can buy them at BIC CAMERA stores.

It’s about 4000JPY and good for 500MB.

You cannnot recharge it. If you would like to use it more, you need to move to a contract.

So it seems like a service to give customers a chance to test their SIM.

For activation, you need to make a call and resister your phone number.

Configuration on your device is also necessary.

So in Japan, still renting SIM or a mobile Wi-Fi router is more popular.



Free Wi-Fi in Tokyo

It’s hard to find good Wi-Fi access in Japan. Why? Please read this.
Japan Times
Simple answer is we don’t need it and we think we should pay for that. If you pay, you can find Wi-Fi everywhere.

However, there are some companies providing free Wi-Fi these days. The list has only major ones.
Seven Eleven shops
Need registration. It seems much easier to resister it at the shops. Just connect their Wi-Fi network in a shop and follow instruction.

This one has good English instruction.

Wired Cafe
Ok, they don’t have English website. Don’t need registration for this one.

I will add links when I find good ones.