The GSM mobile phone system CANNOT be used in Japan. While free Wi-Fi is available at airports and many hotels, it is not typically available on trains or at outdoor tourist attractions. We recommend that you personally arrange for a SIM card or pocket Wi-Fi.
You can purchase a SIM card or contract a digital SIM (eSIM) that can be used in Japan to utilize the services of Japanese telecommunication companies before leaving your country. You can also purchase a SIM card at Narita International Airport after arrival. If you prefer to use wifi instead of a SIM, you can apply for rental wifi before departure and either receive it before departure or pick it up at the airport upon arrival. Find the option that best suits your needs.
Free high speed wireless access is available in the Pacifico Yokohama Conference Center. High speed wireless access is also available in most other hotels in Yokohama, but be sure to check before making reservations.
Given that there is readily available free high speed wireless internet access available to conference attendees, it is recommended that for international attendees they consider setting up a Skype, Google Voice or other internet phone access account, in the unlikely event that they have not already done so, in order to provide themselves more affordable communication with home during the IRG56 meeting.
There are foreign currency exchange centers and ATMs around Narita International Airport and around the Pacifico Yokohama Conference Center, so please make use of them if needed. Nonetheless, most restaurants, convenience stores, hotels, and tourist spots accept not only cash but also credit cards (MasterCard, VISA, JCB).