Xia Yunsheng realized, "So that's why!"
UKS did indeed have this rule, she just didn't think of it at the time, feeling rather unjustified that despite having saved him, he still pointed a gun at her.
However, looking at it from his perspective, and considering her knowledge could jeopardize his future, it's understandable that he should have decisively tried to silence her.
Probably the only reason he didn't go through with it was his fear.
He was probably worried about dealing with the fallout if she was hurt or killed, considering Cheng Yanzhi's interest in her, so he only forced her to sign a guarantee agreement instead.
"So, you really didn't know?" Up until this point, Mo Sichen had been under the assumption that Xia Yunsheng was withholding information from him.
Xia Yunsheng responded, "I just didn't think of it at that moment."
"Can you promise not to tell the Commander? For the sake of Yuchen?"
