You are right Japanese car are much better and efficient than American. To make sure your car was manufactured in japan, look on driver side door..it should be saying -model, year of the car and made in japan instead of Canada or US.  I don't know what kind of car you are buying..auto or manual..but on either case make sure you test drive the car on highway and around city limit areas..look for the car rpm especially on auto and grinding sound on manual..rule of thumb is high rpm without acceleration in speed on automatic and grinding sound when changing gears on manual are not good sign. After test drive, on a parking lot you could look underneath the car for any oil leakage especially on passenger side. Under the hood of the car you could look for transmission oil, belts around the rotors, and another thing that i always look for is exhaust system underneath the car to make sure no tear and wear on muffler cuz bad exhaust system could take extra $300-$500 out of your pocket. If you really want to make sure everything is good on your car than you could take it to your local mechanic and its money worth of spending.