Airsoft isnt very realistic in terms of accurately representing combat.
I play it because it is fun. I think other people have different ideas about fun, so I leave them to decide, even though I would never use something like a C-mag.
And in Japan, people do more than just go to "survival games"
They do quite a bit of indoor shooting competitions, which I havent seen in Canada.
http://gungineer.cande.biz/
And I can say that they are definitely better in gunsmithing than us Canadians.
Some of the custom airsoft and even gun tuning on that site are pretty crazy.
But then again, this is all from talking to people and from reading; I havent actually experienced airsoft in Japan yet...
oh, and since you are in Osaka
check out
http://vietviet.nomaki.jp/
Its next month so you can still make it!
They've got rules on BDU, weapon loadout, ammo, etc