In any case for using the Japan Rail Pass, visitors should arrive to Japan holding a valid temporary visitor's visa for entry of 15 or 90 days of stay. Visitors of more than 68 countries will receive the visa automatically in the arrival to Japan if they visit the country for 90 days or less for any not paid activity. Other nationalities should ask for the temporary visitors visa before arrival to Japan.
Keep in mind that Japan Rail Pass is not possible to be activated in Japan if the visitors is holding a visa that is not the temporary visitor visa for tourism. Having said that, Japan Passport holders won't be able to activate the JRP. We recommend you to make your order not with your Japan Passport.