/s
Between electronic transfer and just settle the debt later, isn’t really an excuse…
You charged a $15usd (~15%) fee when your friend was desperate and willing, when the standard fee for such transactions is at best 0% and worst 5%.
I much prefer zero stress - if money is tight, we just don't do expensive stuff, or steal the bill before they have a chance to pay. Mostly that means we stay cheap until we can safely cover multiple people if needed (running your safety-buffer low enough that you can't do that is a terrible idea anyway).
OP increased the cost of forex from 0-5% to 15% when his "friend" was desperate.
And as you said, "it was an easy 15 bucks". You were very aware of what you were doing: easy money off your "friend", instead of friends not minding a few dollars missing here or there.
He stayed with me for a week last year. We had a big bbq. I stuffed him full of akaushi beef. I didn't ask for a dime, nor would I ever.
I guess you maintain friendships with an excel sheet handy? good for you I guess
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.
(For example, I noticed that if I buy something from Amazon or try to pay for something using Paypal, the exchange rate they offered me is consistently worse than the market rate if I elect to pay with USD instead of JPY. The difference often adds up to a few dollars, even accounting for foreign transaction fees that my bank might charge.)
OP clearly stated the situation was of a mutual benefit - friend got their Y now and don't need to bother with doing an exchange, OP got a few spare bucks which was a such big sum what it literally sat in the drawer for 5 (five) years.