Should I buy an AM/FM tuner from Japan?

No, you shouldn’t, not unless you like listening to a 2 MHz slice of the 20 MHz FM broadcast band!

Japan has a different FM band frequency allocation, spanning 76 – 90 MHz. The Australasian, European and North American FM broadcast band spans 88 – 108 MHz. That means that with a Japanese FM tuner, you’ll see a tiny 2 MHz overlap. You’ll be lucky if you can pick up one station in that slice and this often cannot be changed, especially in the older analog style tuners.