Wait. You live in Tokyo. Are you japanese? Or do you just live there? When did you move?
Anyways.. loosing a friend (or, you didn't really lose her, she just went away) is always really tough and sad. There's really not much you can do to ease the pain, since you guys were such good friends.. But you should keep the contact with her.
And try to get other friends to hang out with - no matter how boring they might seem to you now! I'm sure you'll eventually find that some of your other friends are actually great to spend some time with too! OR you might try and meet some new people.. there are loads of them, and since you're in Tokyo.. there should be SOMEONE out there who's cool to hang out with, or get lost with, or share whatever with...
Hang in there. Don't be too sad... (at least you're in Tokyo...)