Actually, it's not surprising that these two are worried. Nangong Jin has been chasing Di Jinxuan for a really long time—since summer until winter—it's been almost half a year.
In the past, people were afraid he was just fooling around and even threatened to forbid him from eating meat.
But now the two of them are super lovey-dovey. The proposal has been made, and Di Jinxuan has agreed. Essentially, that's as good as being engaged. Li Hui, Nangong Tiancheng, Fang Hao, and Di Yan are already starting to plan the wedding. Letting them sleep together is basically the family's tacit approval that they are now husband and wife.
It's just missing a marriage certificate and the wedding itself, but in the eyes of the family, the two of them are already a done deal.
Logically speaking, after such a long pursuit and mutual affection, shouldn't they have, well, you know, done "that" by now? But apparently, they haven't?
