Hi Joel
Tung oil, it has been used for centuries by the Chinese and Japanese, I
would think also on their nara wood, Lee Valley sells pure tung oil, I
would think that it would be a good choice to use, just take your time,
and let the oil polymerize, before putting on the next coat.
http://homepage.mac.com/l.vanderloo/PhotoAlbum12.html
Have fun and take care
Leo Van Der Loo