Not sure it has anything to do with being expat, just living in a very remote area. I have no idea where exactly Tokushima is but perhaps you can join a club of some sort? I knew expats in Nagano prefecture who randomly became avid mountaineers/climbers just because it is the thing to do there if you want to build a huge local network. It can also be running, cycling, surfing whatever. Even living in a huge city in NA I find it very fun to be part of a club completely unrelated to programming/dev work. I also run just for myself that is kindof a mind defrag for me.

Judging from pictures I would love to just run there, that is one gorgeous place.