I guess the usual techniques for meeting people shall work for you. i.e. going to dance clubs, joining club/circle activities. If your school or university has some sports clubs or international community clubs, it should be worthwhile to pay a visit. I mean, back in my days in university, that was how I met with Japanese as well as foreign friends. Or maybe something like Nagano Rotary Club. I am sure the online community is helpful, but they are supplemental. First-hand information or encounter is always better when it comes to the locality. Too bad your sharehouse sucks. The sharehouse is supposed to be the place to make a totally new connection with totally different kind of people. Or maybe, you can find the other sharehouse. You know there should be more than your current one that has the vacancy... Either way, there definitely are people who really, really want to talk with foreigners, especially in ENGLISH no matter what your skin colour is.
I just did some google surfing and it tells me that Ueda is very interesting place. Weekend trip to mountain or farm should be nice. As you mentioned, there is a lot of stuff to do there. So a little try will get you find some friends for sure.