If you look up Japanese Invasion Currency and Chinese WWII Banknotes there is interesting history to them. Like anything else - they have value to the people who value those kinds of things. There is a facebook page for collectors of these notes. And do note that what is asked on ebaY is often different from what is sold on ebay.
Good info Im sure they have value to some people those are pretty cool to have good luck selling them if thats what you plan to do I would keep them.....
I wish you good luck on your adventure with these notes. I lived in Hakata, Japan for 5 months prior to heading to Vietnam. Loved my time in Hakata, had a good gal there, but Nam called and I never looked back. Sometimes I wonder what happened to that gal, but Life happened to me. She sure was a very sweet person, always wished the best for her.