Originally Posted by
AlwaysAisle
Yes, old notes remain as legal tender in Japan. For example, one yen note which was issued in 1885 still remains legal tender as far as the Japanese government is concerned. As far as the Japanese government is concerned, the 1885 one yen note is still valued as one yen. However, among collectors, the 1885 one yen notes are valued at 35000 yen for an average condition and 120000 yen for a pristine condition.
Glad to hear about the value of these old notes as I have a bunch of 100-yen notes at home along with a few 1-yen notes and a 10-yen note (photographed below). I'll have to have the value of these assessed, as they could be worth a pretty penny with the right dates on them. The U.S. government also recognizes al
l circulating notes issued from 1861 to the present at face value as legal tender. When I was a kid, my grandparents gave me silver dollars as presents on birthdays and on Christmas. I had collected 30 of them over the years but my parents were unwise and deposited them in a bank account for me and all I could get back were relatively worthless federal reserve notes or silver certificates (supposedly redeemable in silver, but no longer so since the 1960s). 
Old Japanese currency notes
After a little searching, I also found this Japanese-Malaya occupation currency (sometimes called "Banana Money") from the first half of the 1940s, a $10 bill printed in English and curiously denominated in "Japanese dollars." I don't think the Japanese government accepts this as legal tender in Japan, but it apparently has some small collector value.
Japanese-Malaya $10 bill printed in English
The reverse side of the $10 bill