Your post is kinda vague whether the vehicle is already in Pakistan or you're planning to select one from Japan and ask Jan Japan to facilitate in importing it.
Purchasing isn't illegal
But the process through vehicle will be imported is by using loopholes in the system
You can look up the actual procedure to import a used vehicle in Pakistan, it's allowed under personal baggage, gift or transfer of residence. Now do u have a friend, relative or family member living abroad who'll pay for the vehicle or is Jan Japan handling that?
What they'll do is use passport of someone living abroad (pay them commission for that) and show that the payment for vehicle wasn't made from Pakistan where infact they can't provide a money trail that your payment went through legal channels from your account to Jan Japan Pakistan's, to their Japanese office and then to the auction house.