If you are struggling mentally please call or see someone in charge of your program to see if there are any resources for emergency mental health services near your location. That may be tricky in Japan but there must be something.
http://www.suicide.org/hotlines/international/japan-suicide-hotlines.html
You could try this site. Even though you don’t mention suicide, these hotlines will have mental health resources for you.
You aren’t complaining. You are struggling and you are reaching out for help. You are engaged in an activity, studying overseas on your own, that is making you vulnerable and at risk. Please tell you parents. Please try the resources on the website.