There are two particularly convenient ways for tourists to connect to the internet in Japan.
Rent a portable Wi-Fi. It is recommended to choose a small modem that can connect multiple devices at once. You can rent it at specialized stores in major airports. However, it is recommended to reserve online in advance to avoid stock issues.
Purchase a prepaid SIM card. You can purchase it at airports, electronics stores, 24-hour stores, and vending machines. Once you insert it into your smartphone or tablet, you can use the internet.
Both methods offer high-speed wireless internet access anywhere in Japan. However, since they are usually data-only, it is recommended to install an application that allows you to make voice calls via the internet.
You can also make voice calls using the international roaming service of your phone company in your home country. However, you will need to dial the international phone prefix (a two- or three-digit number following a plus sign) to call your home country, and (+81) to add to the phone number when calling a Japanese number. However, overseas calls can be expensive, so it is recommended to check your phone company's rates before your trip.
You can also rent a mobile phone at the direct stores of each company at major airports such as Narita Airport and Kansai Airport.
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