Just whereabouts in Japan are you? Can you give me a vague location?
As for your condition, I remember a story about a gaijin who was so worked up in the culture shock that he got himself a pile of steel and welded together a boat. By the time he got over it, he had a 35 foot sailboat to play with.
The remedy is to do something. Excercise, play video games, travel, sing, dance, build a boat, launch a missle, gas some subway stations and write on this forum.
Also, buy beer at discount outlets in 24 can boxes. Imported beer is the cheapest. On a good day you can buy a box of 24 cans for 1300 yen.
Japanese food is generally low on cholesterol. You are not supposed to get cholesterol-deprivation depression until your total cholesterol is below 90, but some people do complain of mild depression on the down side of the slope while the TC is still normal. Put a lot of butter on your foods and eat a lot of bacon for a while until you get used to the low cholesterol diet. It just might do the trick.