Master-disciple relationship
Perhaps, Ling Qingyu should listen to their stories every now and then, to understand them better. They weren't mere characters summoned from the card.
They were living beings, with strong emotions and interests. From several interactions, Ling Qingyu speculated a deal might have made between them and the system but their memories about the agreement was likely to be sealed, because Ling Qingyu had tried to ask but not one could answer.
They were also puzzled. However, one thing calmed their mind. The timeline in their world had been frozen and only after finishing the task, could they return.
Thinking of their possible departure in the future, Ling Qingyu felt reluctant but she was hopeful, world traveling might be a thing too.
Worrying too much about what she couldn't deal or control was meaningless; focusing on the present was better.