Depending on your service provider and plan your mobile phone may be active in Japan. You can also buy SIM cards for data only at the airport and in the local convenience stores such as Lawson and Seicomart. Check that your phone is unlocked and compatible for SIM change before purchasing a data SIM card. Most of our luxury hotels and chalets have wifi - but having your own phone in Japan can be great in a pinch / for the 'gram.