I agree with @NorthernMom61 that you should talk to the local person in charge of your study abroad program. They should be able to put you in contact with a local therapist. Also, it’s really, really good you are reaching out for help. Letting the local program director know will also help you in so far as they should then check in on you periodically to see how you’re doing and help you assess what’s going on. I would think they would also be willing to talk with your parents, if you consent.
I’ve also been to Japan, and although it’s a lovely country and very safe, I had a hard time there because the culture was just so different from what I’m used to. I’m just trying to say that I totally get it. But really, my experience and anyone else’s experience is totally irrelevant. And there is no such thing as “you should feel X”. Dump the guilt. And dump the expectation that you should be feeling a certain way. You’re feeling what you’re feeling and that’s OK. We all just want you to feel better.