I would really appreciate any advice or help on this one.

There's a long story behind this one but ill try and keep it short, i hope the readers can get what im trying to say.

Im a 25 year old guy, went through a bad break up 3 years ago that almost killed me but i got better, my confidence came back and just about got over her.
In April this year I came to Japan to work for 3 months, so i go home in June. I came here and met a fellow British guy and we started going out drinking, we met 2 Japanese girls. I fell in love with mine, actually at the moment ive never been happier, thats the problem. we all went away together for a week, ive taken her out for dinner countless times, we've slept on a beach under the stars, we've literally fallen deeply in love with her and ive now realised I think ive basically killed myself. Im really over-sensitive anyway, but now i realise, we both realise, soon im going to have to say goodbye. I dont know how to take it, even if we both love each other i wont be able to stand being without her, she has already started crying when we talked about me leaving and that nearly set me off, the whole thing is a mess and I really can't see how to come out of this without entering a deep depression. Im lost...