HAHA Yea good, blame on the Gaijins!!
It must be a foreigner. All Japanese would know... that trying to give away money like this is a waste of time
But on the subject of returning money.. Really depends.
I found about 3 wallets, retuned them all.. because they had what tops 100 bucks in it.. but all of the people that got their wallet returned ended up "rewarding" me with some money, so it wasn't a waste.
Finding raw money, with no way to be traced back to whom it is.. I keep around for some time, and if some unluck soul come back looking all over the place I know who the owner is^^
Happened once, outside the bank a guy dropped his paycheck, I found, sat on a bench and just waited (I had to wait my father anyway, stupid bank lines) 5min later some guy come back looking around, I gave back to him..
But, if I open up my mailbox and there is 1m yen.. sorry, that would go straight to my pocket =p
"Chile is a thin and tall country"