1. Since the main card and the auxiliary card of a credit card share the same account, the auxiliary card shares all or part of the credit limit of the main card. No matter which credit card you use to log in to your credit card account, you can see the consumption of another credit card.

2. Two cards in the same account can be returned to any card, no matter which one, as long as the repayment is successful, there is no need to repay separately. However, if both the primary card and the secondary card are not returned, then the primary card holder will bear all responsibilities, such as interest, late fees, bad credit and so on. You don't have to bear the secondary card.