Japan is small country not sure how much the average cars there are driven? But ya very strange that only 5000 km a year driven!!! I bought one ex-embassy 96 in islamabad and right now it has 200,000 km on it.
Its best to look at the car to see whether or not the mileage is genuine, ie paint condition/original or not, specially the bumpers as if they are original you will see if there are dings in the paint or whatever.
Second look at the seats/interior, how springy they are. Condition of glass. Engine bay, underneath car, trunk etc. Steering wheel wear, gear knob. If a car has 50,000 on the meter but the car looks really used then it most likely not true. Use common sense.
Side note Tricky to get these to work on CNG, gave up on mine.