昨年の4月に2週間ほど休暇で帰国した時に利用しました。以下の規定が再度変更されていなければ領事館からの在留証明を提示すれば購入できますよ。（短期の休暇の場合だと思います）帰国する時に書類を持っていくことも忘れないようにしたほうがいいですよ。日本でJR Passを受け取るときに提示を求められるかもしれませんから。

New eligibility requirements for sales of an Exchange Order for JAPAN RAIL PASS starting June 1, 2017
People who have both their Japanese passport and written proof—obtained from the embassy or legation of Japan in the foreign country where they live—that they have been living legally in the country for 10 consecutive years or more
* You must present both your passport and proof of eligibility to purchase an Exchange Order in a country other than Japan, and to exchange your Exchange Order for a JAPAN RAIL PASS in Japan.
* You cannot use a photocopy of your passport to purchase an Exchange Order or to exchange your Exchange Order for a JAPAN RAIL PASS.
* You can purchase an Exchange Order and exchange it for a JAPAN RAIL PASS only if your stay in the country for 10 consecutive years or more is verified by such written proof.
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