I think there’s usually some natural selection that will associate people with common interests. If you behave like the stereotyped “cool dude” you describe, then you will naturally attract to you people who either behave similarly or that are attracted by such behaviour.
But, they aren’t the only kind of people in the world. Sure, they may be quite loud since they tend to be, as you said, somehow charismaric (in their way) and this may lead you to think they are the only way to be, but I’m pretty positive this is not the case.
Think about the people at the dinner we had here in Rome: (almost) everyone had the same interests. Possibly, some of the most active people in the fields you’re interested in (or have been interested in) were at the table.. and how did we meet? How come we ended up together and not just with a bunch of your “cool disco guys”?

Sure, sometimes you may fall in a group of friends that don’t share all your interests (which is not necessarily your case anyway). You may try to keep up with them, to change in order to stick with them or just to try some new experiences.. but in the end you’ll likely start thinking that something’s wrong, and whether that’s what you really want to do..

So, to make a not-so-long story even shorter, I guess one should keep his own beliefs and keep pursuing his goals. That’s something I’m sure you know very well and can actually teach me about! ;)
There’s nothing wrong in trying some new stuff from time to time, but we should be aware of what we’re doing and try not to pretend we’re completely someone else, as it usually doesn’t work out!
There’s also nothing wrong with you wanting to do more of a “japanese life” than a gaijin one, but I guess that will be a progressive thing, not something that can be completely chosen rationally. It’s just a matter of time!

Holy shit, I should really get some more sleep…