International Dating ?

Sounds like she likes you but the way she keeps saying she has to go back, Means she is not thinking of a relationship. But you gotta look at the signs more carefully, Or you could talk to her if you like her too and you wanna start a relationship.
GOOD LUCK

Seems like she just wants a companion friend while she is here. I believe she keeps telling you she is due back in her country so that you don't get the wrong impression. However, because she is Japanese, as I mentioned in another post, Japanese culture is so hard to decipher. Also, as you should know, Japanese are trained not to say no. They will say anything, but no, so when you talk to her, don't ask questions that are geared towards a yes no answer.
In this case, maybe I would ask, 'had you been staying in the USA permanently, what would have been different about our hanging out together and enjoying each other's company? ' What you don't want to ask is, 'had you stayed in the USA permanently, would you have dated me? '

My close friend married a Japanese girl, and it took him about 2 years to finally understand why the girl behaves she does. Tough culture to crack!

Actually, interesting fact. As a kid I used to watch a lot of anime, and in those cartoons you will see a father taking a shower with the little girls. I asked my friend why was that and she said in Japanese culture, specially in the smaller cities, until fairly recent, it was normal for dads to take showers with their daughters, until teenage years or so. I wonder what your friend would comment on the subject! Good luck!