shoobiedoo was now stuck with a locally useless $100 American. So, he was actually given a hassle to resolve of getting it converted back to yen.
If the guy was so hot to not lose a dime, he could have said, “Loan me 10k yen right now, I will pay you back ASAP”.
If the guy is in Japan with American currency, he likely knows the exchange rate and exactly the terms he was getting.