One of the strange things about where I was, was that the after work drinks thing didn't happen. I had thought every Japanese company was indulging in that pastime, but as it turns out mine did not. My company had an End of Year party, welcome new employees party, and end of project party. It was about three time a year we'd see each other outside the office; the rest of the year was 12 hour days or worse.
In the 7 months I worked in US dev last year, we went out 4 or 5 times, and it was always fun, and initiated by the coworkers. I made several new friends, and felt like I could breathe again.
As for language, I'm able to converse pretty handily, though its nowhere near native, or even casual fluency. Even so, I don't feel it's the primary cause preventing intimacy. The likely cause there is a fundamental discrepancy in value systems.
One of the schools I worked at held enkais pretty regularly. They always invited me, even after I quit going (I don't drink, so it was just awkward). I was even invited to go to some hot springs resort for a day or two, for the low LOW price of
only 80,000 yen, which I politely declined. But another school never invited me- when I first got there I invited myself along and it was even more awkward. Turns out that this school had a little clique going and only the people in that group went to the enkais. I don't know what happened after most of them were transferred the following school year.
One time after an enkai, I was asked to go to a snack bar with some other male teachers. When I declined another teacher got in my face and asked me if I was
gay. That was the first and only time he ever said anything to me.
Other teachers grabbed him and took him away, while the English teachers were all "no, no! He has a girlfriend!" I told the guy "yeah, I don't need to go to a loser bar to pay women to talk to me," which got laughs out of the English speakers and seemed to really piss the guy off (he was totally smashed). I think that was the last enkai I went to.
My current job has official events and unofficial going away parties for people, but I never go. I'm an introvert and also tend to not give a shit about any of the people leaving.