What to send to Japan

Remember that everyone mails packages for Christmas. when I was stationed in Germany (87 - 89), I mailed my packages before Thanksgiving. The closer to Christmas the rougher handleing the boxes get and the longer the line to pick up packages.
I'd suggest putting each cookie type in a separate ziplock so even if they crumble you can still eat them with a spoon. Trust me - if he's single and eating cafeteria food even cookie crumbs from home are great!
He may not have access to a stove or oven, I didn't when I was single. I'd keep that in mind with any mixes. Our dorms did have microwaves though and almost all work places also. A favorite snack was microwave popcorn. If you don't have tins for packing maybe use a microwave container. At least that he can reuse.
If he does have access to a stove - One of my sisters favorite gifts was a pot, pudding mixes and a whisk. (We had a dorm size frig for 1 - 4 people).
I agree with the poster that suggested local favorites and favorite brands. I once bought an uncooked Hardee's Ham and Cheese, froze it in tinfoil, and carried it on the plane with me for a friend. Wouldn't suggest that for the mail but it does show how desperate people can get for old favorites! :-)
Maybe a video tape of his favorite sport (commercials too, the one english station we got had Air Force messages in place of commercials) or show. SouthPark is one almost all guys like. My DH (also prior military) always wanted stuff relating to his college football team. Impossible to get out of the country.