Firstly welcome to the forum.
It sounds like you've managed to stumble into something pretty cool. I'm sure others will have more useful stuff to suggest than I will at this point.
The only thing I can think is that rather than hoping fortune continues to smile and they read your post by chance, I'd suggest talking to them directly about it. If they already know you are planning on going away to Japan, find out how they feel about that, and the prospects for pursuing a relationship at this time, or if they'd want to wait, or make the best of the time you have. Perhaps they're having the same discussions themselves. You won't know unless the subject is broached.