Zhai Sheng should have known very well of Qiao Nan's situation. She didn't start being young, having started school today.
Both of them had a secret relationship for years.
Qiao Nan had hidden it very well for the past four years—nobody noticed that they were in a relationship. They hid it very well, as if they were performing a secret service.
On the one hand, it suggested that the two of them were smart enough to be able to hide it from everyone.
On the other hand, it proved that Qiao Nan could handle hardships. Zhai Sheng had to stay in the camp every day, but she did not lose her temper or throw tantrums. Instead, she studied hard at school and had excellent results.
If not for the fact that they were lovey-dovey when they were with each other, Old Master Zhai and Zhai Yaohui would have suspected that they were not in a serious relationship.