In that classic anime Otaku no Video there is one of the 'interviews' with a firearm otaku having a war game with friends. Military and gun otaku and maniacs in Japan are part of the larger mix of fan cultures that exist there.
But what of the U.S? Sure you have heard of paintball, but is there more?
Apparently yes, much more, and they have a magazine. The NAM: National Airsoft Magazine is for hard core fans and hobbyists.
Check it out, even if you are like me and not into guns. These guys are putting out a pretty impressive product.