Others borrowed money to buy a car, but the loan was not paid off. This car was sold to me. Who did the loan company ask for money?

It is illegal to transfer the ownership before the loan is repaid, so the bank will ask the original owner to collect the arrears.

Generally speaking, the vehicle loan needs to be detained in the Green Paper (Vehicle Register). Without the Green Paper, the vehicle cannot be transferred. If it is a private transaction, the original owner can't repay the car loan on time, and the bank or financial institution will apply to the court to detain the car as a lien on arrears. If the payment cannot be made within the time specified by the lender, the vehicle will be auctioned to repay the loan.