Other Processed Foods
Items such as cookies, crackers, candies, cereals, dried noodles, etc., may be brought into Japan. Most types of nuts (with the exception of walnuts, which are prohibited) may be brought into Japan, particularly if they are salted, dried, or roasted.
I was just looking at the customs laws of what I can import into japan and found the wonderful quote above. I would like to believe there is a nice sensible reason why walnuts are considered particularly dangerous, so if anyone knows please tell me.
On the same page I also found I can import 100kg of rice duty free per year, so if anyone coming to visit me has some left over weight allowance how about bringing me a sack? Preferably long grain, and definitely not that nasty non-stick stuff! (try and eat it with chopsticks if you wonder why)