There are no taxes. There are different courses - one in Russia (the central bank), the other in Japan (usually 2-4 yen below). To change the currency to yen in Japan is more profitable only with the sums of more than 50,000 yen, the gain will be about 10-15 usd. We recommend buying some yen in Russia for rubles (choosing the best rate among banks) + taking a plastic card with you.